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Search for "rhodium" in Full Text gives 182 result(s) in Beilstein Journal of Organic Chemistry.
When metal-catalyzed C–H functionalization meets visible-light photocatalysis
- Lucas Guillemard and
- Joanna Wencel-Delord
Beilstein J. Org. Chem. 2020, 16, 1754–1804, doi:10.3762/bjoc.16.147
- described the combination of rhodium and photoredox catalysis for the direct C–H ortho-olefination of arylamides (Figure 7) [74]. The procedure was performed under air at 80 °C and turned out to be efficient using a low loading of a Ru-based photosensitizer. A broad range of DGs could be installed on the
Graphical Abstract
Figure 1: Concept of dual synergistic catalysis.
Figure 2: Classification of catalytic systems involving two catalysts.
Figure 3: General mechanism for the dual nickel/photoredox catalytic system.
Figure 4: General mechanisms for C–H activation catalysis involving different reoxidation strategies.
Figure 5: Indole synthesis via dual C–H activation/photoredox catalysis.
Figure 6: Proposed mechanism for the indole synthesis via dual catalysis.
Figure 7: Oxidative Heck reaction on arenes via the dual catalysis.
Figure 8: Proposed mechanism for the Heck reaction on arenes via dual catalysis.
Figure 9: Oxidative Heck reaction on phenols via the dual catalysis.
Figure 10: Proposed mechanism for the Heck reaction on phenols via dual catalysis.
Figure 11: Carbazole synthesis via dual C–H activation/photoredox catalysis.
Figure 12: Proposed mechanism for the carbazole synthesis via dual catalysis.
Figure 13: Carbonylation of enamides via the dual C–H activation/photoredox catalysis.
Figure 14: Proposed mechanism for carbonylation of enamides via dual catalysis.
Figure 15: Annulation of benzamides via the dual C–H activation/photoredox catalysis.
Figure 16: Proposed mechanism for the annulation of benzamides via dual catalysis.
Figure 17: Synthesis of indoles via the dual C–H activation/photoredox catalysis.
Figure 18: Proposed mechanism for the indole synthesis via dual catalysis.
Figure 19: General concept of dual catalysis merging C–H activation and photoredox catalysis.
Figure 20: The first example of dual catalysis merging C–H activation and photoredox catalysis.
Figure 21: Proposed mechanism for the C–H arylation with diazonium salts via dual catalysis.
Figure 22: Dual catalysis merging C–H activation/photoredox using diaryliodonium salts.
Figure 23: Direct arylation via the dual catalytic system reported by Xu.
Figure 24: Direct arylation via dual catalytic system reported by Balaraman.
Figure 25: Direct arylation via dual catalytic system reported by Guo.
Figure 26: C(sp3)–H bond arylation via the dual Pd/photoredox catalytic system.
Figure 27: Acetanilide derivatives acylation via the dual C–H activation/photoredox catalysis.
Figure 28: Proposed mechanism for the C–H acylation with α-ketoacids via dual catalysis.
Figure 29: Acylation of azobenzenes via the dual catalysis C–H activation/photoredox.
Figure 30: C2-acylation of indoles via the dual C–H activation/photoredox catalysis.
Figure 31: Proposed mechanism for the C2-acylation of indoles with aldehydes via dual catalysis.
Figure 32: C2-acylation of indoles via the dual C–H activation/photoredox catalysis.
Figure 33: Perfluoroalkylation of arenes via the dual C–H activation/photoredox catalysis.
Figure 34: Proposed mechanism for perfluoroalkylation of arenes via dual catalysis.
Figure 35: Sulfonylation of 1-naphthylamides via the dual C–H activation/photoredox catalysis.
Figure 36: Proposed mechanism for sulfonylation of 1-naphthylamides via dual catalysis.
Figure 37: meta-C–H Alkylation of arenes via visible-light metallaphotocatalysis.
Figure 38: Alternative procedure for meta-C–H alkylation of arenes via metallaphotocatalysis.
Figure 39: Proposed mechanism for meta-C–H alkylation of arenes via metallaphotocatalysis.
Figure 40: C–H borylation of arenes via visible-light metallaphotocatalysis.
Figure 41: Proposed mechanism for C–H borylation of arenes via visible-light metallaphotocatalysis.
Figure 42: Undirected C–H aryl–aryl cross coupling via dual gold/photoredox catalysis.
Figure 43: Proposed mechanism for the undirected C–H aryl–aryl cross-coupling via dual catalysis.
Figure 44: Undirected C–H arylation of (hetero)arenes via dual manganese/photoredox catalysis.
Figure 45: Proposed mechanism for the undirected arylation of (hetero)arenes via dual catalysis.
Figure 46: Photoinduced C–H arylation of azoles via copper catalysis.
Figure 47: Photo-induced C–H chalcogenation of azoles via copper catalysis.
Figure 48: Decarboxylative C–H adamantylation of azoles via dual cobalt/photoredox catalysis.
Figure 49: Proposed mechanism for the C–H adamantylation of azoles via dual catalysis.
Figure 50: General mechanisms for the “classical” (left) and Cu-free variant (right) Sonogoshira reaction.
Figure 51: First example of a dual palladium/photoredox catalysis for Sonogashira-type couplings.
Figure 52: Arylation of terminal alkynes with diazonium salts via dual gold/photoredox catalysis.
Figure 53: Proposed mechanism for the arylation of terminal alkynes via dual catalysis.
Figure 54: C–H Alkylation of alcohols promoted by H-atom transfer (HAT).
Figure 55: Proposed mechanism for the C–H alkylation of alcohols promoted by HAT.
Figure 56: C(sp3)–H arylation of latent nucleophiles promoted by H-atom transfer.
Figure 57: Proposed mechanism for the C(sp3)–H arylation of latent nucleophiles promoted by HAT.
Figure 58: Direct α-arylation of alcohols promoted by H-atom transfer.
Figure 59: Proposed mechanism for the direct α-arylation of alcohols promoted by HAT.
Figure 60: C–H arylation of amines via dual Ni/photoredox catalysis.
Figure 61: Proposed mechanism for the C–H arylation of amines via dual Ni/photoredox catalysis.
Figure 62: C–H functionalization of nucleophiles via excited ketone/nickel dual catalysis.
Figure 63: Proposed mechanism for the C–H functionalization enabled by excited ketones.
Figure 64: Selective sp3–sp3 cross-coupling promoted by H-atom transfer.
Figure 65: Proposed mechanism for the selective sp3–sp3 cross-coupling promoted by HAT.
Figure 66: Direct C(sp3)–H acylation of amines via dual Ni/photoredox catalysis.
Figure 67: Proposed mechanism for the C–H acylation of amines via dual Ni/photoredox catalysis.
Figure 68: C–H hydroalkylation of internal alkynes via dual Ni/photoredox catalysis.
Figure 69: Proposed mechanism for the C–H hydroalkylation of internal alkynes.
Figure 70: Alternative procedure for the C–H hydroalkylation of ynones, ynoates, and ynamides.
Figure 71: Allylic C(sp3)–H activation via dual Ni/photoredox catalysis.
Figure 72: Proposed mechanism for the allylic C(sp3)–H activation via dual Ni/photoredox catalysis.
Figure 73: Asymmetric allylation of aldehydes via dual Cr/photoredox catalysis.
Figure 74: Proposed mechanism for the asymmetric allylation of aldehydes via dual catalysis.
Figure 75: Aldehyde C–H functionalization promoted by H-atom transfer.
Figure 76: Proposed mechanism for the C–H functionalization of aldehydes promoted by HAT.
Figure 77: Direct C–H arylation of strong aliphatic bonds promoted by HAT.
Figure 78: Proposed mechanism for the C–H arylation of strong aliphatic bonds promoted by HAT.
Figure 79: Direct C–H trifluoromethylation of strong aliphatic bonds promoted by HAT.
Figure 80: Proposed mechanism for the C–H trifluoromethylation of strong aliphatic bonds.
Pauson–Khand reaction of fluorinated compounds
- Jorge Escorihuela,
- Daniel M. Sedgwick,
- Alberto Llobat,
- Mercedes Medio-Simón,
- Pablo Barrio and
- Santos Fustero
Beilstein J. Org. Chem. 2020, 16, 1662–1682, doi:10.3762/bjoc.16.138
- described, including the use of metals other than cobalt (such as rhodium, iridium, titanium, ruthenium, nickel, and palladium), or the use of CO surrogates such as aldehydes, alcohols and formates. Recently, its utility in flow chemistry has also been described [42]. Intramolecular Pauson–Khand reactions
Graphical Abstract
Scheme 1: Schematic representation of the Pauson–Khand reaction.
Scheme 2: Substrates included in this review.
Scheme 3: Commonly accepted mechanism for the Pauson–Khand reaction.
Scheme 4: Regioselectivity of the PKR.
Scheme 5: Variability at the acetylenic and olefinic counterpart.
Scheme 6: Pauson–Khand reaction of fluoroolefinic enynes reported by the group of Ishizaki [46].
Scheme 7: PKR of enynes bearing fluorinated groups on the alkynyl moiety, reported by the group of Ishizaki [46]....
Scheme 8: Intramolecular PKR of 1,7-enynes reported by the group of Billard [47].
Scheme 9: Intramolecular PKR of 1,7-enynes reported by the group of Billard [48].
Scheme 10: Intramolecular PKR of 1,7-enynes by the group of Bonnet-Delpon [49]. Reaction conditions: i) Co(CO)8 (1...
Scheme 11: Intramolecular PKR of 1,6-enynes reported by the group of Ichikawa [50].
Scheme 12: Intramolecular Rh(I)-catalyzed PKR reported by the group of Hammond [52].
Scheme 13: Intramolecular PKR of allenynes reported by the group of Osipov [53].
Scheme 14: Intramolecular PKR of 1,7-enynes reported by the group of Osipov [53].
Scheme 15: Intramolecular PKR of fluorine-containing 1,6-enynes reported by the Konno group [54].
Scheme 16: Diastereoselective PKR with enantioenriched fluorinated enynes 34 [55].
Scheme 17: Intramolecular PKR reported by the group of Martinez-Solorio [56].
Scheme 18: Fluorine substitution at the olefinic counterpart.
Scheme 19: Synthesis of fluorinated enynes 37 [59].
Scheme 20: Fluorine-containing substrates in PKR [59].
Scheme 21: Pauson Khand reaction for fluorinated enynes by the Fustero group: scope and limitations [59].
Scheme 22: Synthesis of chloro and bromo analogues [59].
Scheme 23: Dimerization pathway [59].
Scheme 24: Synthesis of fluorine-containing N-tethered 1,7-enynes [61].
Scheme 25: Intramolecular PKR of chiral N-tethered fluorinated 1,7-enynes [61].
Scheme 26: Examples of further modifications to the Pauson−Khand adducts [61].
Scheme 27: Asymmetric synthesis the fluorinated enynes 53.
Scheme 28: Intramolecular PKR of chiral N-tethered 1,7-enynes 53 [64].
Scheme 29: Intramolecular PKR of chiral N-tethered 1,7-enyne bearing a vinyl fluoride [64].
Scheme 30: Catalytic intramolecular PKR of chiral N-tethered 1,7-enynes [64].
Scheme 31: Model fluorinated alkynes used by Riera and Fustero [70].
Scheme 32: PKR with norbornadiene and fluorinated alkynes 58 [71].
Scheme 33: Nucleophilic addition/detrifluoromethylation and retro Diels-Alder reactions [70].
Scheme 34: Tentative mechanism for the nucleophilic addition/retro-aldol reaction sequence.
Scheme 35: Catalytic PKR with norbornadiene [70].
Scheme 36: Scope of the PKR of trifluoromethylalkynes with norbornadiene [72].
Scheme 37: DBU-mediated detrifluoromethylation [72].
Scheme 38: A simple route to enone 67, a common intermediate in the total synthesis of α-cuparenone.
Scheme 39: Effect of the olefin partner in the regioselectivity of the PKR with trifluoromethyl alkynes [79].
Scheme 40: Intermolecular PKR of trifluoromethylalkynes with 2-norbornene reported by the group of Konno [54].
Scheme 41: Intermolecular PKR of diarylalkynes with 2-norbornene reported by the group of Helaja [80].
Scheme 42: Intermolecular PKR reported by León and Fernández [81].
Scheme 43: PKR reported with cyclopropene 73 [82].
Recent synthesis of thietanes
- Jiaxi Xu
Beilstein J. Org. Chem. 2020, 16, 1357–1410, doi:10.3762/bjoc.16.116
- functionalized thietanes, electron-deficient sulfur ylides were investigated in the ring expansion of thiiranes. However, the reactions failed due to the poor nucleophilicity of the electron-deficient sulfur ylides. However, in the presence of rhodium catalysts, the electron-deficient sulfur ylides were
Graphical Abstract
Figure 1: Examples of biologically active thietane-containing molecules.
Figure 2: The diverse methods for the synthesis of thietanes.
Scheme 1: Synthesis of 1-(thietan-2-yl)ethan-1-ol (10) from 3,5-dichloropentan-2-ol (9).
Scheme 2: Synthesis of thietanose nucleosides 2,14 from 2,2-bis(bromomethyl)propane-1,3-diol (11).
Scheme 3: Synthesis of methyl 3-vinylthietane-3-carboxylate (19).
Scheme 4: Synthesis of 1,6-thiazaspiro[3.3]heptane (24).
Scheme 5: Synthesis of 6-amino-2-thiaspiro[3.3]heptane hydrochloride (28).
Scheme 6: Synthesis of optically active thietane 31 from vitamin C.
Scheme 7: Synthesis of an optically active thietane nucleoside from diethyl L-tartrate (32).
Scheme 8: Synthesis of thietane-containing spironucleoside 40 from 5-aldo-3-O-benzyl-1,2-O-isopropylidene-α-D...
Scheme 9: Synthesis of optically active 2-methylthietane-containing spironucleoside 43.
Scheme 10: Synthesis of a double-linked thietane-containing spironucleoside 48.
Scheme 11: Synthesis of two diastereomeric thietanose nucleosides via 2,4-di(benzyloxymethyl)thietane (49).
Scheme 12: Synthesis of the thietane-containing PI3k inhibitor candidate 54.
Scheme 13: Synthesis of the spirothietane 57 as the key intermediate to Nuphar sesquiterpene thioalkaloids.
Scheme 14: Synthesis of spirothietane 61 through a direct cyclic thioetherification of 3-mercaptopropan-1-ol.
Scheme 15: Synthesis of thietanes 66 from 1,3-diols 62.
Scheme 16: Synthesis of thietanylbenzimidazolone 75 from (iodomethyl)thiazolobenzimidazole 70.
Scheme 17: Synthesis of 2-oxa-6-thiaspiro[3.3]heptane (80) from bis(chloromethyl)oxetane 76 and thiourea.
Scheme 18: Synthesis of the thietane-containing glycoside, 2-O-p-toluenesulfonyl-4,6-thioanhydro-α-D-gulopyran...
Scheme 19: Synthesis of methyl 4,6-thioanhydro-α-D-glucopyranoside (89).
Scheme 20: Synthesis of thietane-fused α-D-galactopyranoside 93.
Scheme 21: Synthesis of thietane-fused α-D-gulopyranoside 100.
Scheme 22: Synthesis of 3,5-anhydro-3-thiopentofuranosides 104.
Scheme 23: Synthesis of anhydro-thiohexofuranosides 110, 112 and 113 from from 1,2:4,5-di-O-isopropylidene D-f...
Scheme 24: Synthesis of optically active thietanose nucleosides from D- and L-xyloses.
Scheme 25: Synthesis of thietane-fused nucleosides.
Scheme 26: Synthesis of 3,5-anhydro-3-thiopentofuranosides.
Scheme 27: Synthesis of 2-amino-3,5-anhydro-3-thiofuranoside 141.
Scheme 28: Synthesis of thietane-3-ols 145 from (1-chloromethyl)oxiranes 142 and hydrogen sulfide.
Scheme 29: Synthesis of thietane-3-ol 145a from chloromethyloxirane (142a).
Scheme 30: Synthesis of thietane-3-ols 145 from 2-(1-haloalkyl)oxiranes 142 and 147 with ammonium monothiocarb...
Scheme 31: Synthesis of 7-deoxy-5(20)thiapaclitaxel 154a, a thietane derivative of taxoids.
Scheme 32: Synthesis of 5(20)-thiadocetaxel 158 from 10-deacetylbaccatin III (155).
Scheme 33: Synthesis of thietane derivatives 162 as precursors for deoxythiataxoid synthesis through oxiraneme...
Scheme 34: Synthesis of 7-deoxy 5(20)-thiadocetaxel 154b.
Scheme 35: Mechanism for the formation of the thietane ring in 171 from oxiranes with vicinal leaving groups 1...
Scheme 36: Synthesis of cis-2,3-disubstituted thietane 175 from thiirane-2-methanol 172.
Scheme 37: Synthesis of a bridged thietane 183 from aziridine cyclohexyl tosylate 179 and ammonium tetrathiomo...
Scheme 38: Synthesis of thietanes via the photochemical [2 + 2] cycloaddition of thiobenzophenone 184a with va...
Scheme 39: Synthesis of spirothietanes through the photo [2 + 2] cycloaddition of cyclic thiocarbonyls with ol...
Scheme 40: Photochemical synthesis of spirothietane-thioxanthenes 210 from thioxanthenethione (208) and butatr...
Scheme 41: Synthesis of thietanes 213 from 2,4,6-tri(tert-butyl)thiobenzaldehyde (211) with substituted allene...
Scheme 42: Photochemical synthesis of spirothietanes 216 and 217 from N-methylthiophthalimide (214) with olefi...
Scheme 43: Synthesis of fused thietanes from quadricyclane with thiocarbonyl derivatives 219.
Scheme 44: Synthesis of tricyclic thietanes via the photo [2 + 2] cycloaddition of N-methyldithiosuccinimides ...
Scheme 45: Synthesis of tricyclic thietanes via the photo [2 + 2] cycloaddition of N-methylthiosuccinimide/thi...
Scheme 46: Synthesis of tricyclic thietanes via the photo [2 + 2] cycloaddition of N-alkylmonothiophthalimides...
Scheme 47: Synthesis of spirothietanes from dithiosuccinimides 223 with 2,3-dimethyl-2-butene (215a).
Scheme 48: Synthesis of thietanes 248a,b from diaryl thione 184b and ketene acetals 247a,b.
Scheme 49: Photocycloadditions of acridine-9-thiones 249 and pyridine-4(1H)-thione (250) with 2-methylacrynitr...
Scheme 50: Synthesis of thietanes via the photo [2 + 2] cycloaddition of mono-, di-, and trithiobarbiturates 2...
Scheme 51: Synthesis of spirothietanes via the photo [2 + 2] cycloaddition of 1,1,3-trimethyl-2-thioxo-1,2-dih...
Scheme 52: Synthesis of spirothietanes via the photo [2 + 2] cycloaddition of thiocoumarin 286 with olefins.
Scheme 53: Photochemical synthesis of thietanes 296–299 from semicyclic and acyclic thioimides 292–295 and 2,3...
Scheme 54: Photochemical synthesis of spirothietane 301 from 1,3,3-trimethylindoline-2-thione (300) and isobut...
Scheme 55: Synthesis of spirobenzoxazolethietanes 303 via the photo [2 + 2] cycloaddition of alkyl and aryl 2-...
Scheme 56: Synthesis of spirothietanes from tetrahydrothioxoisoquinolines 306 and 307 with olefins.
Scheme 57: Synthesis of spirothietanes from 1,3-dihydroisobenzofuran-1-thiones 311 and benzothiophene-1-thione...
Scheme 58: Synthesis of 2-triphenylsilylthietanes from phenyl triphenylsilyl thioketone (316) with electron-po...
Scheme 59: Diastereoselective synthesis of spiropyrrolidinonethietanes 320 via the photo [2 + 2] cycloaddition...
Scheme 60: Synthesis of bicyclic thietane 323 via the photo [2 + 2] cycloaddition of 2,4-dioxo-3,4-dihydropyri...
Scheme 61: Photo-induced synthesis of fused thietane-2-thiones 325 and 326 from silacyclopentadiene 324 and ca...
Scheme 62: Synthesis of highly strained tricyclic thietanes 328 via the intramolecular photo [2 + 2] cycloaddi...
Scheme 63: Synthesis of tri- and pentacyclic thietanes 330 and 332, respectively, through the intramolecular p...
Scheme 64: Synthesis of tricyclic thietanes 334 via the intramolecular photo [2 + 2] cycloaddition of N-vinylt...
Scheme 65: Synthesis of tricyclic thietanes 336 via the intramolecular photo [2 + 2] cycloaddition of N-but-3-...
Scheme 66: Synthesis of tricyclic thietanes via the intramolecular photo [2 + 2] cycloaddition of N-but-3-enyl...
Scheme 67: Synthesis of tetracyclic thietane 344 through the intramolecular photo [2 + 2] cycloaddition of N-[...
Scheme 68: Synthesis of tri- and tetracyclic thietanes 348, 350, and 351, through the intramolecular photo [2 ...
Scheme 69: Synthesis of tetracyclic fused thietane 354 via the photo [2 + 2] cycloaddition of vinyl 2-thioxo-3H...
Scheme 70: Synthesis of highly rigid thietane-fused β-lactams via the intramolecular photo [2 + 2] cycloadditi...
Scheme 71: Asymmetric synthesis of a highly rigid thietane-fused β-lactam 356a via the intramolecular photo [2...
Scheme 72: Diastereoselective synthesis of the thietane-fused β-lactams via the intramolecular photo [2 + 2] c...
Scheme 73: Asymmetric synthesis of thietane-fused β-lactams 356 via the intramolecular photo [2 + 2] cycloaddi...
Scheme 74: Synthesis of the bridged bis(trifluoromethyl)thietane from 2,2,4,4-tetrakis(trifluoromethyl)-1,3-di...
Scheme 75: Synthesis of the bridged-difluorothietane 368 from 2,2,4,4-tetrafluoro-1,3-dithietane (367) and qua...
Scheme 76: Synthesis of bis(trifluoromethyl)thietanes from 2,2,4,4-tetrakis(trifluoromethyl)-1,3-dithietane (3...
Scheme 77: Synthesis of 2,2-dimethylthio-4,4-di(trifluoromethyl)thietane (378) from 2,2,4,4-tetrakis(trifluoro...
Scheme 78: Formation of bis(trifluoromethyl)thioacetone (381) through nucleophilic attack of dithietane 363 by...
Scheme 79: Synthesis of 2,2-bis(trifluoromethyl)thietanes from 2,2,4,4-tetrakis(trifluoromethyl)-1,3-dithietan...
Scheme 80: Synthesis of the bridged bis(trifluoromethyl)thietane 364 from of 2,2,4,4-tetrakis(trifluoromethyl)...
Scheme 81: Synthesis of 2,4-diiminothietanes 390 from alkenimines and 4-methylbenzenesulfonyl isothiocyanate (...
Scheme 82: Synthesis of arylidene 2,4-diiminothietanes 393 starting from phosphonium ylides 391 and isothiocya...
Scheme 83: Synthesis of thietane-2-ylideneacetates 397 through a DABCO-catalyzed formal [2 + 2] cycloaddition ...
Scheme 84: Synthesis of 3-substituted thietanes 400 from (1-chloroalkyl)thiiranes 398.
Scheme 85: Synthesis of N-(thietane-3-yl)azaheterocycles 403 and 404 through reaction of chloromethylthiirane (...
Scheme 86: Synthesis of 3-sulfonamidothietanes 406 from sulfonamides and chloromethylthiirane (398a).
Scheme 87: Synthesis of N-(thietane-3-yl)isatins 408 from chloromethylthiirane (398a) and isatins 407.
Scheme 88: Synthesis of 3-(nitrophenyloxy)thietanes 410 from nitrophenols 409 and chloromethylthiirane (398a).
Scheme 89: Synthesis of N-aryl-N-(thietane-3-yl)cyanamides 412 from N-arylcyanamides 411 and chloromethylthiir...
Scheme 90: Synthesis of 1-(thietane-3-yl)pyrimidin-2,4(1H,3H)-diones 414 from chloromethylthiirane (398a) and ...
Scheme 91: Synthesis of 2,4-diiminothietanes 418 from 2-iminothiiranes 416 and isocyanoalkanes 415.
Scheme 92: Synthesis of 2-vinylthietanes 421 from thiiranes 419 and 3-chloroallyl lithium (420).
Scheme 93: Synthesis of thietanes from thiiranes 419 and trimethyloxosulfonium iodide 424.
Scheme 94: Mechanism for synthesis of thietanes 425 from thiiranes 419 and trimethyloxosulfonium iodide 424.
Scheme 95: Synthesis of functionalized thietanes from thiiranes and dimethylsulfonium acylmethylides.
Scheme 96: Mechanism for the rhodium-catalyzed synthesis of functionalized thietanes 429 from thiiranes 419 an...
Scheme 97: Synthesis of 3-iminothietanes 440 through thermal isomerization from 4,5-dihydro-1,3-oxazole-4-spir...
Scheme 98: Synthesis of thietanes 443 from 3-chloro-2-methylthiolane (441) through ring contraction.
Scheme 99: Synthesis of an optically active thietanose 447 from D-xylose involving a ring contraction.
Scheme 100: Synthesis of optically thietane 447 via the DAST-mediated ring contraction of 448.
Scheme 101: Synthesis of the optically thietane nucleoside 451 via the ring contraction of thiopentose in 450.
Scheme 102: Synthesis of spirothietane 456 from 3,3,5,5-tetramethylthiolane-2,4-dithione (452) and benzyne (453...
Scheme 103: Synthesis of thietanes 461 via photoisomerization of 2H,6H-thiin-3-ones 459.
Scheme 104: Phosphorodithioate-mediated synthesis of 1,4-diarylthietanes 465.
Scheme 105: Mechanism of the phosphorodithioate-mediated synthesis of 1,4-diarylthietanes 465.
Scheme 106: Phosphorodithioate-mediated synthesis of trisubstituted thietanes (±)-470.
Scheme 107: Mechanism on the phosphorodithioate-mediated synthesis of trisubstituted thietanes.
Scheme 108: Phosphorodithioate-mediated synthesis of thietanes (±)-475.
Scheme 109: Phosphorodithioate-mediated synthesis of 1,2-disubstituted thietanes from aldehydes 476 and acrylon...
Scheme 110: Phosphorodithioate-mediated synthesis of 1,2-disubstituted thietanes via a one-pot three-component ...
Scheme 111: Mechanism for the phosphorodithioate-mediated synthesis of 1,2-disubstituted thietanes via three-co...
Scheme 112: Phosphorodithioate-mediated synthesis of substituted 3-nitrothietanes.
Scheme 113: Mechanism on the phosphorodithioate-mediated synthesis of 1,2-disubstituted thietanes (±)-486.
Scheme 114: Asymmetric synthesis of (S)-2-phenylthietane (497).
Scheme 115: Asymmetric synthesis of optically active 2,4-diarylthietanes.
Scheme 116: Synthesis of 3-acetamidothietan-2-one 503 via the intramolecular thioesterification of 3-mercaptoal...
Scheme 117: Synthesis of 4-substituted thietan-2-one via the intramolecular thioesterification of 3-mercaptoalk...
Scheme 118: Synthesis of 4,4-disubstituted thietan-2-one 511 via the intramolecular thioesterification of the 3...
Scheme 119: Synthesis of a spirothietan-2-one 514 via the intramolecular thioesterification of 3-mercaptoalkano...
Scheme 120: Synthesis of thiatetrahydrolipstatin starting from (S)-(−)-epichlorohydrin ((S)-142a).
Scheme 121: Synthesis of 2-phenethyl-4-(propan-2-ylidene)thietane (520) from 5-bromo-6-methyl-1-phenylhept-5-en...
Scheme 122: Synthesis of 2-phenethyl-4-(propan-2-ylidene)thietane (520) directly from S-(5-bromo-6-methyl-1-phe...
Scheme 123: Synthesis of 2-alkylidenethietanes from S-(2-bromoalk-1-en-4-yl)thioacetates.
Scheme 124: Synthesis of 2-alkylidenethietanes from S-(2-bromo/chloroalk-1-en-4-yl)thiols.
Scheme 125: Synthesis of spirothietan-3-ol 548 from enone 545 and ammonium hydrosulfide.
Scheme 126: Asymmetric synthesis of the optically active thietanoside from cis-but-2-ene-1,4-diol (47).
Scheme 127: Synthesis of 2-alkylidenethietan-3-ols 557 via the fluoride-mediated cyclization of thioacylsilanes ...
Scheme 128: Synthesis of 2-iminothietanes via the reaction of propargylbenzene (558) and isothiocyanates 560 in...
Scheme 129: Synthesis of 2-benzylidenethietane 567 via the nickel complex-catalyzed electroreductive cyclizatio...
Scheme 130: Synthesis of 2-iminothietanes 569 via the photo-assisted electrocyclic reaction of N-monosubstitute...
Scheme 131: Synthesis of ethyl 3,4-diiminothietane-2-carboxylates from ethyl thioglycolate (570) and bis(imidoy...
Scheme 132: Synthesis of N-(thietan-3-yl)-α-oxoazaheterocycles from azaheterocyclethiones and chloromethyloxira...
Scheme 133: Synthesis of thietan-3-yl benzoate (590) via the nickel-catalyzed intramolecular reductive thiolati...
Scheme 134: Synthesis of 2,2-bis(trifluoromethyl)thietane from 3,3-bis(trifluoromethyl)-1,2-dithiolane.
Scheme 135: Synthesis of thietanes from enamines and sulfonyl chlorides.
Scheme 136: Synthesis of spirothietane 603 via the [2 + 3] cycloaddition of 2,2,4,4-tetramethylcyclobutane-1,3-...
Scheme 137: Synthesis of thietane (605) from 1-bromo-3-chloropropane and sulfur.
Recent applications of porphyrins as photocatalysts in organic synthesis: batch and continuous flow approaches
- Rodrigo Costa e Silva,
- Luely Oliveira da Silva,
- Aloisio de Andrade Bartolomeu,
- Timothy John Brocksom and
- Kleber Thiago de Oliveira
Beilstein J. Org. Chem. 2020, 16, 917–955, doi:10.3762/bjoc.16.83
- HEH were used as H donors for both the benzyl and thiyl radicals, respectively. The HEH was needed to avoid the dimerization of the thiophenol to the disulfide (Scheme 11). Fu and co-workers have demonstrated the huge versatility of rhodium porphyrins for photocatalysis. In 2015, they showed that the
- hydration of terminal alkynes to ketones can be photocatalyzed by rhodium(III) tetrakis(p-sulfonylphenyl)porphyrin (RhIIITSPP) [37]. The coupling between RhIII(TSPP) and terminal alkynes produced the β-carbonylalkylrhodium porphyrin as a photoactive intermediate, whose irradiation produced the PhCOCH2
- highly regioselective photoinduced hydro-defluorination of perfluoroarenes with RhIII(TSPP) [38]. The oxidative addition of the perfluoroarene to the metal complex furnished the active rhodium aryl complex intermediate, which led to the product after visible light irradiation. The hydro-defluorination
Graphical Abstract
Figure 1: Chemical structures of the porphyrinoids and their absorption spectra: in bold are highlighted the ...
Figure 2: Photophysical and photochemical processes (Por = porphyrin). Adapted from [12,18].
Figure 3: Main dual photocatalysts and their oxidative/reductive excited state potentials, including porphyri...
Scheme 1: Photoredox alkylation of aldehydes with diazo acetates using porphyrins and a Ru complex. aUsing a ...
Scheme 2: Proposed mechanism for the alkylation of aldehydes with diazo acetates in the presence of TPP.
Scheme 3: Arylation of heteroarenes with aryldiazonium salts using TPFPP as photocatalyst, and corresponding ...
Scheme 4: A) Scope with different aryldiazonium salts and enol acetates. B) Photocatalytic cycles and compari...
Scheme 5: Photoarylation of isopropenyl acetate A) Comparison between batch and continuous-flow approaches an...
Scheme 6: Dehalogenation induced by red light using thiaporphyrin (STPP).
Scheme 7: Applications of NiTPP as both photoreductant and photooxidant.
Scheme 8: Proposed mechanism for obtaining tetrahydroquinolines by reductive quenching.
Scheme 9: Selenylation and thiolation of anilines.
Scheme 10: NiTPP as photoredox catalyst in oxidative and reductive quenching, in comparison with other photoca...
Scheme 11: C–O bond cleavage of 1-phenylethanol using a cobalt porphyrin (CoTMPP) under visible light.
Scheme 12: Hydration of terminal alkynes by RhIII(TSPP) under visible light irradiation.
Scheme 13: Regioselective photocatalytic hydro-defluorination of perfluoroarenes by RhIII(TSPP).
Scheme 14: Formation of 2-methyl-2,3-dihydrobenzofuran by intramolecular hydro-functionalization of allylpheno...
Scheme 15: Photocatalytic oxidative hydroxylation of arylboronic acids using UNLPF-12 as heterogeneous photoca...
Scheme 16: Photocatalytic oxidative hydroxylation of arylboronic acids using MOF-525 as heterogeneous photocat...
Scheme 17: Preparation of the heterogeneous photocatalyst CNH.
Scheme 18: Photoinduced sulfonation of alkenes with sulfinic acid using CNH as photocatalyst.
Scheme 19: Sulfonic acid scope of the sulfonation reactions.
Scheme 20: Regioselective sulfonation reaction of arimistane.
Scheme 21: Synthesis of quinazolin-4-(3H)-ones.
Scheme 22: Selective photooxidation of aromatic benzyl alcohols to benzaldehydes using Pt/PCN-224(Zn).
Scheme 23: Photooxidation of benzaldehydes to benzoic acids using Pt or Pd porphyrins.
Scheme 24: Photocatalytic reduction of various nitroaromatics using a Ni-MOF.
Scheme 25: Photoinduced cycloadditions of CO2 with epoxides by MOF1.
Figure 4: Electronic configurations of the species of oxygen. Adapted from [66].
Scheme 26: TPP-photocatalyzed generation of 1O2 and its application in organic synthesis. Adapted from [67-69].
Scheme 27: Pericyclic reactions involving singlet oxygen and their mechanisms. Adapted from [67].
Scheme 28: First scaled up ascaridole preparation from α-terpinene.
Scheme 29: Antimalarial drug synthesis using an endoperoxidation approach.
Scheme 30: Photooxygenation of colchicine.
Scheme 31: Synthesis of (−)-pinocarvone from abundant (+)-α-pinene.
Scheme 32: Seeberger’s semi-synthesis of artemisinin.
Scheme 33: Synthesis of artemisinin using TPP and supercritical CO2.
Scheme 34: Synthesis of artemisinin using chlorophyll a.
Scheme 35: Quercitol stereoisomer preparation.
Scheme 36: Photocatalyzed preparation of naphthoquinones.
Scheme 37: Continuous endoperoxidation of conjugated dienes and subsequent rearrangements leading to oxidized ...
Scheme 38: The Opatz group total synthesis of (–)-oxycodone.
Scheme 39: Biomimetic syntheses of rhodonoids A, B, E, and F.
Scheme 40: α-Photooxygenation of chiral aldehydes.
Scheme 41: Asymmetric photooxidation of indanone β-keto esters by singlet oxygen using PTC as a chiral inducer...
Scheme 42: Asymmetric photooxidation of both β-keto esters and β-keto amides by singlet oxygen using PTC-2 as ...
Scheme 43: Bifunctional photo-organocatalyst used for the asymmetric oxidation of β-keto esters and β-keto ami...
Scheme 44: Mechanism of singlet oxygen oxidation of sulfides to sulfoxides.
Scheme 45: Controlled oxidation of sulfides to sulfoxides using protonated porphyrins as photocatalysts. aIsol...
Scheme 46: Photochemical oxidation of sulfides to sulfoxides using PdTPFPP as photocatalyst.
Scheme 47: Controlled oxidation of sulfides to sulfoxides using SnPor@PAF as a photosensitizer.
Scheme 48: Syntheses of 2D-PdPor-COF and 3D-Pd-COF.
Scheme 49: Photocatalytic oxidation of A) thioanisole to methyl phenyl sulfoxide and B) various aryl sulfides,...
Scheme 50: General mechanism for oxidation of amines to imines.
Scheme 51: Oxidation of secondary amines to imines.
Scheme 52: Oxidation of secondary amines using Pd-TPFPP as photocatalyst.
Scheme 53: Oxidative amine coupling using UNLPF-12 as heterogeneous photocatalyst.
Scheme 54: Synthesis of Por-COF-1 and Por-COF-2.
Scheme 55: Photocatalytic oxidation of amines to imines by Por-COF-2.
Scheme 56: Photocyanation of primary amines.
Scheme 57: Synthesis of ᴅ,ʟ-tert-leucine hydrochloride.
Scheme 58: Photocyanation of catharanthine and 16-O-acetylvindoline using TPP.
Scheme 59: Photochemical α-functionalization of N-aryltetrahydroisoquinolines using Pd-TPFPP as photocatalyst.
Scheme 60: Ugi-type reaction with 1,2,3,4-tetrahydroisoquinoline using molecular oxygen and TPP.
Scheme 61: Ugi-type reaction with dibenzylamines using molecular oxygen and TPP.
Scheme 62: Mannich-type reaction of tertiary amines using PdTPFPP as photocatalyst.
Scheme 63: Oxidative Mannich reaction using UNLPF-12 as heterogeneous photocatalyst.
Scheme 64: Transformation of amines to α-cyanoepoxides and the proposed mechanism.
Rhodium-catalyzed reductive carbonylation of aryl iodides to arylaldehydes with syngas
- Zhenghui Liu,
- Peng Wang,
- Zhenzhong Yan,
- Suqing Chen,
- Dongkun Yu,
- Xinhui Zhao and
- Tiancheng Mu
Beilstein J. Org. Chem. 2020, 16, 645–656, doi:10.3762/bjoc.16.61
- pressure, cheap ligand and low metal dosage could significantly improve the practicability in both chemical researches and industrial applications. Keywords: cost-effective ligand; industrial catalysis; reductive carbonylation; rhodium catalyst; syngas; Introduction The exploration of environmentally
- chemical industry by offering a practical synthetic tool for the conversion of aryl iodides to arylaldehydes. Results and Discussion Effects of Rh species Rhodium salts coordinated with proper ligands have been reported to be able to realize the activation of CO and H2 and thus might achieve the reductive
- all with halogen anions), but also structural differences (e.g., crystal water, RhCl3 vs RhCl3·3H2O) of analogous Rh salts played an important role in the catalytic synthesis of benzaldehyde. Among all tested rhodium salts, RhCl3·3H2O afforded benzaldehyde in the highest yield and was chosen as the
Graphical Abstract
Figure 1: Rhodium-catalyzed reductive carbonylation of iodobenzene with CO and H2 to afford benzaldehyde. a) ...
Scheme 1: Scaled-up experiment of the reductive carbonylation of iodobenzene to benzaldehyde under the optimi...
Scheme 2: Catalytic species participating in the catalytic process.
Scheme 3: Substrate scope for the Rh-catalyzed reductive carbonylation of aryl iodides using CO and H2. React...
Scheme 4: Isotope-labeling experiments.
Scheme 5: Proposed reaction mechanism for the Rh-catalyzed reductive carbonylation of aryl iodides using CO a...
Preparation and in situ use of unstable N-alkyl α-diazo-γ-butyrolactams in RhII-catalyzed X–H insertion reactions
- Maria Eremeyeva,
- Daniil Zhukovsky,
- Dmitry Dar’in and
- Mikhail Krasavin
Beilstein J. Org. Chem. 2020, 16, 607–610, doi:10.3762/bjoc.16.55
- formation, in various RhII-catalyzed X–H insertion reactions, particularly the recently described rhodium carbene insertion into O–H [1], N–H [2] and S–H [3] bonds of alcohols, aromatic amines, and thiols, respectively. Herein, we report the results of these studies. Results and Discussion Three N-alkyl-α
Graphical Abstract
Figure 1: Previously reported uses of α-diazo-γ-butyrolactams 1 and 4.
Scheme 1: Generation and in situ RhII-catalyzed X–H insertion reactions of the diazo compounds 4a–c. Conditio...
Scheme 2: Formation of the enamine coupling products 8a and b.
Recent developments in photoredox-catalyzed remote ortho and para C–H bond functionalizations
- Rafia Siddiqui and
- Rashid Ali
Beilstein J. Org. Chem. 2020, 16, 248–280, doi:10.3762/bjoc.16.26
- dependence on external oxidants and harsh reaction conditions [83][84]. In this context, in 2014, Fabry et al. reported the use of novel dual photoredox catalytic systems made up of photoredox catalyst 11 and a rhodium catalyst to carry out the Weinreb amide C–H olefination shown in Scheme 1 [85]. By using
Graphical Abstract
Figure 1: List of photoredox catalysts used for C–H bond functionalizations.
Figure 2: List of metal-based photoredox catalysts used in this review article.
Figure 3: Jablonski diagram.
Figure 4: Photoredox catalysis via reductive or oxidative pathways. D = donor, A = acceptor, S = substrate, P...
Figure 5: Schematic representation of the combination of photoredox catalysis and transition metal catalysis.
Scheme 1: Weinreb amide C–H olefination.
Figure 6: Mechanism for the formation of 21 from 19 using photoredox catalyst 11.
Scheme 2: C–H olefination of phenolic ethers.
Scheme 3: Decarboxylative acylation of acetanilides.
Figure 7: Mechanism for the formation of 30 from acetanilide derivatives.
Scheme 4: Synthesis of fluorenone derivatives by intramolecular deoxygenative acylation of biaryl carboxylic ...
Figure 8: Mechanism for the photoredox-catalyzed synthesis of fluorenone derivatives.
Scheme 5: Synthesis of benzothiazoles via aerobic C–H thiolation.
Figure 9: Plausible mechanism for the construction of benzothiazoles from benzothioamides.
Scheme 6: Synthesis of benzothiazoles via oxidant-free C–H thiolation.
Figure 10: Mechanism involved in the synthesis of benzothiazoles via oxidant-free C–H thiolation.
Scheme 7: Synthesis of indoles via C–H cyclization of anilides with alkynes.
Scheme 8: Preparation of 3-trifluoromethylcoumarins via C–H cyclization of arylpropiolate esters.
Figure 11: Mechanistic pathway for the synthesis of coumarin derivatives via C–H cyclization.
Scheme 9: Monobenzoyloxylation without chelation assistance.
Figure 12: Plausible mechanism for the formation of 71 from 70.
Scheme 10: Aryl-substituted arenes prepared by inorganic photoredox catalysis using 12a.
Figure 13: Proposed mechanism for C–H arylations in the presence of 12a and a Pd catalyst.
Scheme 11: Arylation of purines via dual photoredox catalysis.
Scheme 12: Arylation of substituted arenes with an organic photoredox catalyst.
Scheme 13: C–H trifluoromethylation.
Figure 14: Proposed mechanism for the trifluoromethylation of 88.
Scheme 14: Synthesis of benzo-3,4-coumarin derivatives.
Figure 15: Plausible mechanism for the synthesis of substituted coumarins.
Scheme 15: Oxidant-free oxidative phosphonylation.
Figure 16: Mechanism proposed for the phosphonylation reaction of 100.
Scheme 16: Nitration of anilines.
Figure 17: Plausible mechanism for the nitration of aniline derivatives via photoredox catalysis.
Scheme 17: Synthesis of carbazoles via intramolecular amination.
Figure 18: Proposed mechanism for the formation of carbazoles from biaryl derivatives.
Scheme 18: Synthesis of substituted phenols using QuCN.
Figure 19: Mechanism for the synthesis of phenol derivatives with photoredox catalyst 8.
Scheme 19: Synthesis of substituted phenols with DDQ (5).
Figure 20: Possible mechanism for the generation of phenols with the aid of photoredox catalyst 5.
Scheme 20: Aerobic bromination of arenes using an acridinium-based photocatalyst.
Scheme 21: Aerobic bromination of arenes with anthraquinone.
Figure 21: Proposed mechanism for the synthesis of monobrominated compounds.
Scheme 22: Chlorination of benzene derivatives with Mes-Acr-MeClO4 (2).
Figure 22: Mechanism for the synthesis of 131 from 132.
Scheme 23: Chlorination of arenes with 4CzIPN (5a).
Figure 23: Plausible mechanism for the oxidative photocatalytic monochlorination using 5a.
Scheme 24: Monofluorination using QuCN-ClO4 (8).
Scheme 25: Fluorination with fluorine-18.
Scheme 26: Aerobic amination with acridinium catalyst 3a.
Figure 24: Plausible mechanism for the aerobic amination using acridinium catalyst 3a.
Scheme 27: Aerobic aminations with semiconductor photoredox catalyst 18.
Scheme 28: Perfluoroalkylation of arenes.
Scheme 29: Synthesis of benzonitriles in the presence of 3a.
Figure 25: Plausible mechanism for the synthesis of substituted benzonitrile derivatives in the presence of 3a....
Iodine-mediated hydration of alkynes on keto-functionalized scaffolds: mechanistic insight and the regiospecific hydration of internal alkynes
- Zachary Lee,
- Brandon R. Jones,
- Nyochembeng Nkengbeza,
- Michael Phillips,
- Kayla Valentine,
- Alexis Stewart,
- Brandon Sellers,
- Nicholas Shuber and
- Karelle S. Aiken
Beilstein J. Org. Chem. 2019, 15, 2747–2752, doi:10.3762/bjoc.15.265
- extremely harmful to environmental and biological systems [3]. In light of mercury’s toxicity, the synthetic community has given much attention to the use of less harmful reagents. Success has been obtained with many other transition metal salts, for example, palladium(II) [4][5], rhodium(III) [6], copper
Graphical Abstract
Scheme 1: Proposed mechanism for the iodine-mediated hydration of terminal alkynes 1 [15].
Figure 1: 1H NMR investigations on the iodine-mediated hydration of 8 (the range of 1.75–5.25 ppm is displaye...
Figure 2: 1H—13C HSQC spectrum for α-iodo intermediate 9 in CD3CN in the range of 0.90–5.00 ppm (for 1H NMR s...
Scheme 2: Possible outcomes of the iodine-mediated hydration of asymmetric, internal alkynes with neighboring...
Scheme 3: Iodine-mediated hydration of asymmetric, internal alkynes 11a–e.
Combining the Ugi-azide multicomponent reaction and rhodium(III)-catalyzed annulation for the synthesis of tetrazole-isoquinolone/pyridone hybrids
- Gerardo M. Ojeda,
- Prabhat Ranjan,
- Pavel Fedoseev,
- Lisandra Amable,
- Upendra K. Sharma,
- Daniel G. Rivera and
- Erik V. Van der Eycken
Beilstein J. Org. Chem. 2019, 15, 2447–2457, doi:10.3762/bjoc.15.237
- rhodium(III)-catalyzed intermolecular annulation has been established for the preparation of tetrazole-isoquinolone/pyridone hybrids. Several N-acylaminomethyltetrazoles were reacted with arylacetylenes to form the hybrid products in moderate to very good yields. The method relies on the capacity of the
- rhodium catalyst to promote C(sp2)–H activation in the presence of a suitable directing group. The Ugi-azide reaction provides broad molecular diversity and enables the introduction of the tetrazole moiety, which may further assist the catalytic reaction by coordinating the metal center. The scope of the
- activation of the N-benzamidomethyltetrazole core followed by isoquinolone-ring formation to furnish 4a. We endeavored two catalytic systems based on ruthenium and rhodium, which in our laboratory have proven success in this type of cyclization [32][48]. First, the alkynylation protocol was attempted using
Graphical Abstract
Figure 1: Bioactive molecules containing a tetrazole, pyridone or isoquinolone ring.
Scheme 1: Approaches for the synthesis of tetrazoles and isoquinolones and their interplay as designed in thi...
Scheme 2: Scope of the Ugi-azide-4CR/deprotection/acylation sequence. Ugi-azide-4CR conducted at the 2.0 mmol...
Scheme 3: Influence of substituents R and R2 on the reaction outcome. For compounds 4k–m the overall yield in...
Scheme 4: Influence of the alkyne and R1 substituent on the reaction outcome.
Scheme 5: Scope of acrylic, heterocyclic and ring-fused N-acylaminomethyl tetrazole substrates.
Scheme 6: Proposed reaction mechanism using substrates 1a and 3a.
Photochromic diarylethene ligands featuring 2-(imidazol-2-yl)pyridine coordination site and their iron(II) complexes
- Andrey G. Lvov,
- Max Mörtel,
- Anton V. Yadykov,
- Frank W. Heinemann,
- Valerii Z. Shirinian and
- Marat M. Khusniyarov
Beilstein J. Org. Chem. 2019, 15, 2428–2437, doi:10.3762/bjoc.15.235
- their complexes with rhodium(I) [18], platinum(II) [30], and iridium(III) [31] were reported. In contrast, in our work, the 2-(imidazol-2-yl)pyridine unit is used as a heterocyclic moiety of diarylethenes with cyclopentenone, cyclopentene, and cyclohexenone ethene bridges. The novel ligands have been
Graphical Abstract
Figure 1: Families of diarylethene-bases ligands with spatial proximity of coordination site (blue) and photo...
Scheme 1: Synthesis of photochromic ligands.
Figure 2: Electronic spectra of diarylethene 6 upon UV irradiation (313 nm, toluene, c = 3.4 × 10−5 M). Inset...
Scheme 2: Reversible photocyclization of ligand 6.
Figure 3: Molecular structure of complexes 8 (top) and 9 (bottom) at 100 K. The H atoms are omitted for clari...
Figure 4: Variable temperature χT product (blue) and χ (green) of 8 (top) and 9 (bottom) measured at an exter...
Attempted synthesis of a meta-metalated calix[4]arene
- Christopher D. Jurisch and
- Gareth E. Arnott
Beilstein J. Org. Chem. 2019, 15, 1996–2002, doi:10.3762/bjoc.15.195
- ) and rhodium(III) complexes underwent spontaneous, chemoselective cyclometalation via C–H bond activation of the N-bound phenyl group (see Figure 2) [19]. Incorporation of a mesoionic carbene directing group onto the upper rim of a calix[4]arene therefore offered potential for a new route to calix[4
Graphical Abstract
Figure 1: Inherent chirality generated by meta-substitution – the two structures are non-superposable mirror ...
Figure 2: General approach by Albrecht for MIC directed cyclometalation via C–H activation; M = Ru(II), Ir(II...
Figure 3: Concept of cyclometalated calix[4]arene target.
Scheme 1: Synthesis of model mesoionic carbene 5.
Scheme 2: Attempted Ullmann-coupling to give monoazide 7.
Scheme 3: Synthesis of monoazidocalix[4]arene 7 under optimized conditions.
Scheme 4: Synthesis of the putative calix[4]arene mesoionic carbene ruthenium complex 13.
Figure 4: High-resolution mass spectrum (ESI+) of putative ruthenacycle calix[4]arene 13.
A review of the total syntheses of triptolide
- Xiang Zhang,
- Zaozao Xiao and
- Hongtao Xu
Beilstein J. Org. Chem. 2019, 15, 1984–1995, doi:10.3762/bjoc.15.194
- -ring system; palladium-catalyzed carbonylation and in situ lactone formation, and rhodium(II)-catalyzed double bond migration to construct the D-ring; and palladium-catalyzed Csp2–H oxygenation to install the C-14 hydroxy group. In 2016, Qin and co-workers developed a catalytic asymmetric route toward
Graphical Abstract
Figure 1: Structures of triptolide (1), triptonide (2), tripdiolide (3), 16-hydroxytriptolide (4), triptrioli...
Figure 2: Syntheses of triptolide.
Scheme 1: Berchtold’s synthesis of triptolide.
Scheme 2: Li’s formal synthesis of triptolide.
Scheme 3: van Tamelen’s asymmetric synthesis of triptonide and triptolide.
Scheme 4: Van Tamelen’s (method II) formal synthesis of triptolide.
Scheme 5: Sherburn’s formal synthesis of triptolide.
Scheme 6: van Tamelen’s biogenetic type total synthesis of triptolide.
Scheme 7: Yang’s total synthesis of triptolide.
Scheme 8: Key intermediates or transformations of routes J–N.
Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage
- Gagandeep Kour Reen,
- Ashok Kumar and
- Pratibha Sharma
Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165
- associated with the reported methodologies. Amongst various reported TMs, the participation of copper as the catalyst has been used in the largest number of cases followed by the use of palladium, rhodium, and others. It has been further observed that lanthanum, scandium, and vanadium have been very seldomly
- easy recovery and reusability [69]. The role of rhodium in synthetic chemistry Rhodium in the form of Wilkinsons catalyst [RhCl(PPh3)3] played a major role in the field of catalysis [70]. Rhodium is capable of catalyzing a number of organic reactions viz., heterocyclic alkylation and arylation with a
Graphical Abstract
Figure 1: Various drugs having IP nucleus.
Figure 2: Participation percentage of various TMs for the syntheses of IPs.
Scheme 1: CuI–NaHSO4·SiO2-catalyzed synthesis of imidazo[1,2-a]pyridines.
Scheme 2: Experimental examination of reaction conditions.
Scheme 3: One-pot tandem reaction for the synthesis of 2-haloimidazopyridines.
Scheme 4: Mechanistic scheme for the synthesis of 2-haloimidazopyridine.
Scheme 5: Copper-MOF-catalyzed three-component reaction (3-CR) for imidazo[1,2-a]pyridines.
Scheme 6: Mechanism for copper-MOF-driven synthesis.
Scheme 7: Heterogeneous synthesis via titania-supported CuCl2.
Scheme 8: Mechanism involving oxidative C–H functionalization.
Scheme 9: Heterogeneous synthesis of IPs.
Scheme 10: One-pot regiospecific synthesis of imidazo[1,2-a]pyridines.
Scheme 11: Vinyl azide as an unprecedented substrate for imidazo[1,2-a]pyridines.
Scheme 12: Radical pathway.
Scheme 13: Cu(I)-catalyzed transannulation approach for imidazo[1,5-a]pyridines.
Scheme 14: Plausible radical pathway for the synthesis of imidazo[1,5-a]pyridines.
Scheme 15: A solvent-free domino reaction for imidazo[1,2-a]pyridines.
Scheme 16: Cu-NPs-mediated synthesis of imidazo[1,2-a]pyridines.
Scheme 17: CuI-catalyzed synthesis of isoxazolylimidazo[1,2-a]pyridines.
Scheme 18: Functionalization of 4-bromo derivative via Sonogashira coupling reaction.
Scheme 19: A plausible reaction pathway.
Scheme 20: Cu(I)-catalyzed intramolecular oxidative C–H amidation reaction.
Scheme 21: One-pot synthetic reaction for imidazo[1,2-a]pyridine.
Scheme 22: Plausible reaction mechanism.
Scheme 23: Cu(OAc)2-promoted synthesis of imidazo[1,2-a]pyridines.
Scheme 24: Mechanism for aminomethylation/cycloisomerization of propiolates with imines.
Scheme 25: Three-component synthesis of imidazo[1,2-a]pyridines.
Figure 3: Scope of pyridin-2(1H)-ones and acetophenones.
Scheme 26: CuO NPS-promoted A3 coupling reaction.
Scheme 27: Cu(II)-catalyzed C–N bond formation reaction.
Scheme 28: Mechanism involving Chan–Lam/Ullmann coupling.
Scheme 29: Synthesis of formyl-substituted imidazo[1,2-a]pyridines.
Scheme 30: A tandem sp3 C–H amination reaction.
Scheme 31: Probable mechanistic approach.
Scheme 32: Dual catalytic system for imidazo[1,2-a]pyridines.
Scheme 33: Tentative mechanism.
Scheme 34: CuO/CuAl2O4/ᴅ-glucose-promoted 3-CCR.
Scheme 35: A tandem CuOx/OMS-2-based synthetic strategy.
Figure 4: Biomimetic catalytic oxidation in the presence of electron-transfer mediators (ETMs).
Scheme 36: Control experiment.
Scheme 37: Copper-catalyzed C(sp3)–H aminatin reaction.
Scheme 38: Reaction of secondary amines.
Scheme 39: Probable mechanistic pathway.
Scheme 40: Coupling reaction of α-azidoketones.
Scheme 41: Probable pathway.
Scheme 42: Probable mechanism with free energy calculations.
Scheme 43: MCR for cyanated IP synthesis.
Scheme 44: Substrate scope for the reaction.
Scheme 45: Reaction mechanism.
Scheme 46: Probable mechanistic pathway for Cu/ZnAl2O4-catalyzed reaction.
Scheme 47: Copper-catalyzed double oxidative C–H amination reaction.
Scheme 48: Application towards different coupling reactions.
Scheme 49: Reaction mechanism.
Scheme 50: Condensation–cyclization approach for the synthesis of 1,3-diarylated imidazo[1,5-a]pyridines.
Scheme 51: Optimized reaction conditions.
Scheme 52: One-pot 2-CR.
Scheme 53: One-pot 3-CR without the isolation of chalcone.
Scheme 54: Copper–Pybox-catalyzed cyclization reaction.
Scheme 55: Mechanistic pathway catalyzed by Cu–Pybox complex.
Scheme 56: Cu(II)-promoted C(sp3)-H amination reaction.
Scheme 57: Wider substrate applicability for the reaction.
Scheme 58: Plausible reaction mechanism.
Scheme 59: CuI assisted C–N cross-coupling reaction.
Scheme 60: Probable reaction mechanism involving sp3 C–H amination.
Scheme 61: One-pot MCR-catalyzed by CoFe2O4/CNT-Cu.
Scheme 62: Mechanistic pathway.
Scheme 63: Synthetic scheme for 3-nitroimidazo[1,2-a]pyridines.
Scheme 64: Plausible mechanism for CuBr-catalyzed reaction.
Scheme 65: Regioselective synthesis of halo-substituted imidazo[1,2-a]pyridines.
Scheme 66: Synthesis of 2-phenylimidazo[1,2-a]pyridines.
Scheme 67: Synthesis of diarylated compounds.
Scheme 68: CuBr2-mediated one-pot two-component oxidative coupling reaction.
Scheme 69: Decarboxylative cyclization route to synthesize 1,3-diarylimidazo[1,5-a]pyridines.
Scheme 70: Mechanistic pathway.
Scheme 71: C–H functionalization reaction of enamines to produce diversified heterocycles.
Scheme 72: A plausible mechanism.
Scheme 73: CuI-promoted aerobic oxidative cyclization reaction of ketoxime acetates and pyridines.
Scheme 74: CuI-catalyzed pathway for the formation of imidazo[1,2-a]pyridine.
Scheme 75: Mechanistic pathway.
Scheme 76: Mechanistic rationale for the synthesis of products.
Scheme 77: Copper-catalyzed synthesis of vinyloxy-IP.
Scheme 78: Regioselective product formation with propiolates.
Scheme 79: Proposed mechanism for vinyloxy-IP formation.
Scheme 80: Regioselective synthesis of 3-hetero-substituted imidazo[1,2-a]pyridines with different reaction su...
Scheme 81: Mechanistic pathway.
Scheme 82: CuI-mediated synthesis of 3-formylimidazo[1,2-a]pyridines.
Scheme 83: Radical pathway for 3-formylated IP synthesis.
Scheme 84: Pd-catalyzed urea-cyclization reaction for IPs.
Scheme 85: Pd-catalyzed one-pot-tandem amination and intramolecular amidation reaction.
Figure 5: Scope of aniline nucleophiles.
Scheme 86: Pd–Cu-catalyzed Sonogashira coupling reaction.
Scheme 87: One-pot amide coupling reaction for the synthesis of imidazo[4,5-b]pyridines.
Scheme 88: Urea cyclization reaction for the synthesis of two series of pyridines.
Scheme 89: Amidation reaction for the synthesis of imidazo[4,5-b]pyridines.
Figure 6: Amide scope.
Scheme 90: Pd NPs-catalyzed 3-component reaction for the synthesis of 2,3-diarylated IPs.
Scheme 91: Plausible mechanistic pathway for Pd NPs-catalyzed MCR.
Scheme 92: Synthesis of chromenoannulated imidazo[1,2-a]pyridines.
Scheme 93: Mechanism for the synthesis of chromeno-annulated IPs.
Scheme 94: Zinc oxide NRs-catalyzed synthesis of imidazo[1,2-a]azines/diazines.
Scheme 95: Zinc oxide-catalyzed isocyanide based GBB reaction.
Scheme 96: Reaction pathway for ZnO-catalyzed GBB reaction.
Scheme 97: Mechanistic pathway.
Scheme 98: ZnO NRs-catalyzed MCR for the synthesis of imidazo[1,2-a]azines.
Scheme 99: Ugi type GBB three-component reaction.
Scheme 100: Magnetic NPs-catalyzed synthesis of imidazo[1,2-a]pyridines.
Scheme 101: Regioselective synthesis of 2-alkoxyimidazo[1,2-a]pyridines catalyzed by Fe-SBA-15.
Scheme 102: Plausible mechanistic pathway for the synthesis of 2-alkoxyimidazopyridine.
Scheme 103: Iron-catalyzed synthetic approach.
Scheme 104: Iron-catalyzed aminooxygenation reaction.
Scheme 105: Mechanistic pathway.
Scheme 106: Rh(III)-catalyzed double C–H activation of 2-substituted imidazoles and alkynes.
Scheme 107: Plausible reaction mechanism.
Scheme 108: Rh(III)-catalyzed non-aromatic C(sp2)–H bond activation–functionalization for the synthesis of imid...
Scheme 109: Reactivity and selectivity of different substrates.
Scheme 110: Rh-catalyzed direct C–H alkynylation by Li et al.
Scheme 111: Suggested radical mechanism.
Scheme 112: Scandium(III)triflate-catalyzed one-pot reaction and its mechanism for the synthesis of benzimidazo...
Scheme 113: RuCl3-assisted Ugi-type Groebke–Blackburn condensation reaction.
Scheme 114: C-3 aroylation via Ru-catalyzed two-component reaction.
Scheme 115: Regioselective synthetic mechanism.
Scheme 116: La(III)-catalyzed one-pot GBB reaction.
Scheme 117: Mechanistic approach for the synthesis of imidazo[1,2-a]pyridines.
Scheme 118: Synthesis of imidazo[1,2-a]pyridine using LaMnO3 NPs under neat conditions.
Scheme 119: Mechanistic approach.
Scheme 120: One-pot 3-CR for regioselective synthesis of 2-alkoxy-3-arylimidazo[1,2-a]pyridines.
Scheme 121: Formation of two possible products under optimization of the catalysts.
Scheme 122: Mechanistic strategy for NiFe2O4-catalyzed reaction.
Scheme 123: Two-component reaction for synthesizing imidazodipyridiniums.
Scheme 124: Mechanistic scheme for the synthesis of imidazodipyridiniums.
Scheme 125: CuI-catalyzed arylation of imidazo[1,2-a]pyridines.
Scheme 126: Mechanism for arylation reaction.
Scheme 127: Cupric acetate-catalyzed double carbonylation approach.
Scheme 128: Radical mechanism for double carbonylation of IP.
Scheme 129: C–S bond formation reaction catalyzed by cupric acetate.
Scheme 130: Cupric acetate-catalyzed C-3 formylation approach.
Scheme 131: Control experiments for signifying the role of DMSO and oxygen.
Scheme 132: Mechanism pathway.
Scheme 133: Copper bromide-catalyzed CDC reaction.
Scheme 134: Extension of the substrate scope.
Scheme 135: Plausible radical pathway.
Scheme 136: Transannulation reaction for the synthesis of imidazo[1,5-a]pyridines.
Scheme 137: Plausible reaction pathway for denitrogenative transannulation.
Scheme 138: Cupric acetate-catalyzed C-3 carbonylation reaction.
Scheme 139: Plausible mechanism for regioselective C-3 carbonylation.
Scheme 140: Alkynylation reaction at C-2 of 3H-imidazo[4,5-b]pyridines.
Scheme 141: Two-way mechanism for C-2 alkynylation of 3H-imidazo[4,5-b]pyridines.
Scheme 142: Palladium-catalyzed SCCR approach.
Scheme 143: Palladium-catalyzed Suzuki coupling reaction.
Scheme 144: Reaction mechanism.
Scheme 145: A phosphine free palladium-catalyzed synthesis of C-3 arylated imidazopyridines.
Scheme 146: Palladium-mediated Buchwald–Hartwig cross-coupling reaction.
Figure 7: Structure of the ligands optimized.
Scheme 147: Palladium acetate-catalyzed direct arylation of imidazo[1,2-a]pyridines.
Scheme 148: Palladium acetate-catalyzed mechanistic pathway.
Scheme 149: Palladium acetate-catalyzed regioselective arylation reported by Liu and Zhan.
Scheme 150: Mechanism for selective C-3 arylation of IP.
Scheme 151: Pd(II)-catalyzed alkenylation reaction with styrenes.
Scheme 152: Pd(II)-catalyzed alkenylation reaction with acrylates.
Scheme 153: A two way mechanism.
Scheme 154: Double C–H activation reaction catalyzed by Pd(OAc)2.
Scheme 155: Probable mechanism.
Scheme 156: Palladium-catalyzed decarboxylative coupling.
Scheme 157: Mechanistic cycle for decarboxylative arylation reaction.
Scheme 158: Ligand-free approach for arylation of imidazo[1,2-a]pyridine-3-carboxylic acids.
Scheme 159: Mechanism for ligandless arylation reaction.
Scheme 160: NHC-Pd(II) complex assisted arylation reaction.
Scheme 161: C-3 arylation of imidazo[1,2-a]pyridines with aryl bromides catalyzed by Pd(OAc)2.
Scheme 162: Pd(II)-catalyzed C-3 arylations with aryl tosylates and mesylates.
Scheme 163: CDC reaction for the synthesis of imidazo[1,2-a]pyridines.
Scheme 164: Plausible reaction mechanism for Pd(OAc)2-catalyzed synthesis of imidazo[1,2-a]pyridines.
Scheme 165: Pd-catalyzed C–H amination reaction.
Scheme 166: Mechanism for C–H amination reaction.
Scheme 167: One-pot synthesis for 3,6-di- or 2,3,6-tri(hetero)arylimidazo[1,2-a]pyridines.
Scheme 168: C–H/C–H cross-coupling reaction of IPs and azoles catalyzed by Pd(II).
Scheme 169: Mechanistic cycle.
Scheme 170: Rh-catalyzed C–H arylation reaction.
Scheme 171: Mechanistic pathway for C–H arylation of imidazo[1,2-a]pyridine.
Scheme 172: Rh(III)-catalyzed double C–H activation of 2-phenylimidazo[1,2-a]pyridines and alkynes.
Scheme 173: Rh(III)-catalyzed mechanistic pathway.
Scheme 174: Rh(III)-mediated oxidative coupling reaction.
Scheme 175: Reactions showing functionalization of the product obtained by the group of Kotla.
Scheme 176: Mechanism for Rh(III)-catalyzed oxidative coupling reaction.
Scheme 177: Rh(III)-catalyzed C–H activation reaction.
Scheme 178: Mechanistic cycle.
Scheme 179: Annulation reactions of 2-arylimidazo[1,2-a]pyridines and alkynes.
Scheme 180: Two-way reaction mechanism for annulations reaction.
Scheme 181: [RuCl2(p-cymene)]2-catalyzed C–C bond formation reaction.
Scheme 182: Reported reaction mechanism.
Scheme 183: Fe(III) catalyzed C-3 formylation approach.
Scheme 184: SET mechanism-catalyzed by Fe(III).
Scheme 185: Ni(dpp)Cl2-catalyzed KTC coupling.
Scheme 186: Pd-catalyzed SM coupling.
Scheme 187: Vanadium-catalyzed coupling of IP and NMO.
Scheme 188: Mechanistic cycle.
Scheme 189: Selective C3/C5–H bond functionalizations by mono and bimetallic systems.
Scheme 190: rGO-Ni@Pd-catalyzed C–H bond arylation of imidazo[1,2-a]pyridine.
Scheme 191: Mechanistic pathway for heterogeneously catalyzed arylation reaction.
Scheme 192: Zinc triflate-catalyzed coupling reaction of substituted propargyl alcohols.
A novel three-component reaction between isocyanides, alcohols or thiols and elemental sulfur: a mild, catalyst-free approach towards O-thiocarbamates and dithiocarbamates
- András György Németh,
- György Miklós Keserű and
- Péter Ábrányi-Balogh
Beilstein J. Org. Chem. 2019, 15, 1523–1533, doi:10.3762/bjoc.15.155
- isocyanides and sulfur [76] can be enhanced using various catalysts such as selenium, molybdenum, copper, rhodium [77][78][79][80][81][82] or tellurium [83] providing the isothiocyanates in excellent yields. These approaches on the other hand suffer from the use of heavy metals, toxic chalcogens and/or long
Graphical Abstract
Scheme 1: Synthetic routes to O-thiocarbamates and dithiocarbamates.
Scheme 2: Substrate scope of isocyanides. aReaction conditions: 1 (1 mmol), S8 (2 mmol), 2a (2mmol), NaH (2 m...
Scheme 3: Substrate scope of alcohols. Reaction conditions: 1a (1 mmol), S8 (2 mmol), 2 (2mmol), NaH (2 mmol)...
Scheme 4: Substrate scope of thiols. Reaction conditions: 1a (1 mmol), S8 (1.2 mmol), 4 (2 mmol), NaOH (2 mmo...
Scheme 5: Scaled-up synthesis for 3a.
Scheme 6: Multicomponent domino synthesis of quinazolinone 7.
Scheme 7: Control experiments.
Scheme 8: Proposed mechanism.
Selective detection of DABCO using a supramolecular interconversion as fluorescence reporter
- Indrajit Paul,
- Debabrata Samanta,
- Sudhakar Gaikwad and
- Michael Schmittel
Beilstein J. Org. Chem. 2019, 15, 1371–1378, doi:10.3762/bjoc.15.137
- Information File 1, Figure S21) to satisfy maximum site occupancy. Upon the addition of 2 equiv of rhodium porphyrin 3 [37], DABCO was selectively removed from complex 12 [38] affording the sandwich complex 7 = [(3)2(4)] leaving complex 11 untouched and liberating two equiv of 10 (incomplete self-sorting
- , Scheme 2). This phenomenon is readily explained considering the stronger binding of rhodium porphyrin 3 to DABCO (Δlog β = 2.40) compared with zinc porphyrin (Supporting Information File 1, Figure S22). With this ligand shuffling in mind, we wanted to probe the guest-induced double self-sorting depicted
- , DABCO is a highly selective trigger for the structural rearrangement of rectangle 5 to sandwich complex 6. Finally, we tested the reversibility of the system by addition and removal of DABCO using rhodium porphyrin 3 as scavenger of DABCO. In line with the results of the model self-sorting scenarios in
Graphical Abstract
Figure 1: Molecular structures of ligands 1, 2, 3, and 4 and of the resulting products, i.e., rectangle 5, sa...
Scheme 1: Guest addition/removal and reversible interconversion between supramolecular architectures.
Scheme 2: Completive and incomplete self-sorting in presence of copper(I) and rhodium complex 3.
Figure 2: Comparison of partial 1H NMR spectra (400 MHz, CD2Cl2, 298 K) of (a) ligand 2; (b) ligand 1; (c) po...
Figure 3: (a) UV–vis titration of rectangle 5 (2.98 μM) with DABCO (4); (b) several reversible cycles of inte...
Scheme 3: The high selectivity for DABCO in the transformation.
Figure 4: Partial spectra (400 MHz, CD2Cl2, 298 K) showing the reversible switching between rectangle and san...
Alkylation of lithiated dimethyl tartrate acetonide with unactivated alkyl halides and application to an asymmetric synthesis of the 2,8-dioxabicyclo[3.2.1]octane core of squalestatins/zaragozic acids
- Herman O. Sintim,
- Hamad H. Al Mamari,
- Hasanain A. A. Almohseni,
- Younes Fegheh-Hassanpour and
- David M. Hodgson
Beilstein J. Org. Chem. 2019, 15, 1194–1202, doi:10.3762/bjoc.15.116
- area have recently culminated in two communicated syntheses of 6,7-dideoxysqualestatin H5 (DDSQ (2), Figure 1) [12][13]. The centrepiece of both of these strategies is a rhodium(II)-catalysed tandem carbon ylide formation from a diazoketone 3 (Scheme 1) and stereoselective [3 + 2] cycloaddition with a
Graphical Abstract
Figure 1: Squalestatin S1/zaragozic acid A (1) and DDSQ (2).
Scheme 1: Carbonyl ylide cycloaddition–rearrangement to the squalestatin core [12,13].
Scheme 2: Tartrate alkylation strategy to cycloaddition substrate.
Scheme 3: Conversion of α-ketoester to α-diazoester.
Scheme 4: Seebach’s tartrate alkylation and rationalisation of stereoselectivity [17-19].
Scheme 5: Tartrate alkylation with a non-activated alkyl iodide.
Scheme 6: Alkylated tartrate to diazoester sequence.
Scheme 7: TES protection approach to the squalestatin core.
Scheme 8: Tartrate acetonide methylation.
Scheme 9: Tartrate alkylation with various alkyl halides.
Scheme 10: Rationalisation of dialkylation observations.
Scheme 11: Tartrate alkylation chemistry with more complex alkyl iodides [12,13].
Figure 2: Natural product examples containing the monoalkylated tartaric acid motif.
Scheme 12: Epimerisation of monoalkylated tartrates.
Intramolecular cascade annulation triggered by rhodium(III)-catalyzed sequential C(sp2)–H activation and C(sp3)–H amination
- Liangliang Song,
- Guilong Tian,
- Johan Van der Eycken and
- Erik V. Van der Eycken
Beilstein J. Org. Chem. 2019, 15, 571–576, doi:10.3762/bjoc.15.52
- Macromolecular Chemistry, Ghent University, Krijgslaan 281 (S.4), B-9000 Ghent, Belgium Peoples’ Friendship University of Russia (RUDN University), Miklukho-Maklaya Street 6, Moscow, Russia 10.3762/bjoc.15.52 Abstract A rhodium(III)-catalyzed intramolecular oxidative annulation of O-substituted N
- activation; rhodium; acrylamide; heterocycles; Introduction Over the last decade, transition metal-catalyzed C(sp2)–H activation has emerged as an efficient strategy to access complex molecules [1][2][3][4][5][6]. Among the methodologies, RhIII-catalyzed oxidative annulation of a C(sp2)–H bond with 2π
- (Scheme 1b) [29][30][31]. Inspired by this work, we envisaged that tricyclic indolizinones could be built through rhodium(III)-catalyzed sequential C(sp2)–H activation and C(sp3)–H amination of O-substituted N-hydroxyacrylamides (Scheme 1c). Results and Discussion We selected N-hydroxyacrylamide 1a as our
Graphical Abstract
Figure 1: Selected examples of natural products with a tricyclic indolizinone scaffold.
Scheme 1: Previous work and this approach.
Scheme 2: Reaction scope. Reaction conditions: 1 (0.3 mmol), [RhCp*Cl2]2 (0.015 mmol), CsOAc (0.6 mmol), 1,4-...
Scheme 3: Control experiments.
Scheme 4: Proposed mechanism.
Dirhodium(II)-catalyzed [3 + 2] cycloaddition of N-arylaminocyclopropane with alkyne derivatives
- Wentong Liu,
- Yi Kuang,
- Zhifan Wang,
- Jin Zhu and
- Yuanhua Wang
Beilstein J. Org. Chem. 2019, 15, 542–550, doi:10.3762/bjoc.15.48
- cycloaddition chemistry based on compound 1. Zheng et al. [7] first reported on the [3 + 2] cycloaddition reaction of 1 with an alkene or alkyne mediated by visible light by the aid of the photocatalyst [Ru(bpz)3](PF6)2. Our group reported the metal catalyst itself, particularly the dinuclear rhodium complex
- study the cycloaddition in dichloromethane (DCM) with 1 mol % starting catalyst loading under the previously reported conditions [18]. In the absence of a catalyst, no cycloaddition product 3a formed (Table 1, entry 1). We then studied the effect of common rhodium catalysts on the reactions. When 1 mol
Graphical Abstract
Scheme 1: Applications of N-arylaminocyclopropanes.
Scheme 2: Synthesis of trans-ethyl 2-aminocyclopentanecarboxylate.
Scheme 3: Proposed mechanism.
Syntheses and chemical properties of β-nicotinamide riboside and its analogues and derivatives
- Mikhail V. Makarov and
- Marie E. Migaud
Beilstein J. Org. Chem. 2019, 15, 401–430, doi:10.3762/bjoc.15.36
- ]. Many of these complexes contain rhodium or iridium coordinated with fully (methyl)substituted cyclopentadienyl ligands and bis-coordinating diamino ligands as shown in Figure 7. The reducing agent may be a formate anion as a source of hydride, triethanolamine as an electron donor in the case of
Graphical Abstract
Figure 1: Structural formulas of Nam, NA, NR+, NMN, and NAD+.
Figure 2: Main synthetic routes to nicotinamide riboside (NR+X−).
Scheme 1: Synthesis of NR+Cl− based on the reaction of peracylated chlorosugars with Nam.
Figure 3: Predominant formation of β-anomer over α-anomer of NR+X−.
Scheme 2: Synthesis of NR+Cl− by reacting 3,5-di-O-benzoyl-D-ribofuranosyl chloride (5) with Nam (1a).
Figure 4: Mechanism of the formation of the β-anomer of the glycosylated product in the case of the reaction ...
Scheme 3: Synthesis of NR+Br− by reacting bromosugars with Nam (1a).
Scheme 4: Synthesis of NR+OTf− based on the glycosylation of Nam (1a) with tetra-O-acetyl-β-D-ribofuranose (2a...
Scheme 5: Improved synthesis of NR+OTfˉ and NAR+OTfˉ based on the glycosylation of pre-silylated Nam or NA wi...
Scheme 6: Synthesis of triacetylated NAR+OTf− by glycosylation of nicotinic acid trimethylsilyl ester with te...
Scheme 7: Synthesis of NR+Cl− from NR+OTf− by means of ion exchange with sodium chloride solution.
Scheme 8: Synthesis of acylated NR+OTf− by means of ion exchange with sodium chloride.
Scheme 9: Synthesis of triacetylated derivatives of NAR+ by glycosylation of nicotinic acid esters with ribos...
Scheme 10: Synthesis of NR+OTf− from the triflate salt of ethyl nicotinate-2,3,5-triacetyl-β-D-riboside in met...
Scheme 11: Reaction of 2,3,5-tri-O-acetyl-β-phenyl nicotinate riboside triflate salt with secondary and tertia...
Scheme 12: Synthesis of NMN based on the Zincke reaction of N-(2,4-dinitrophenyl)-3-carbamoylpyridinium chlori...
Scheme 13: Synthesis of NMN based on the Zincke reaction of N-(2,4-dinitrophenyl)-3-carbamoylpyridinium chlori...
Scheme 14: Efficacious protection of 2′,3′-hydroxy groups of NR+X−.
Scheme 15: Protection of the 2′,3′-hydroxy groups of NR+Cl– with a mesitylmethylene acetal group.
Figure 5: Reduction of derivatives of NR+Xˉ into corresponding 1,2-; 1,4-; 1,6-NRH derivatives.
Figure 6: Mechanism of the reduction of the pyridinium core with dithionite as adapted from [67].
Scheme 16: Reduction of triacylated NR+OTf– derivatives by sodium dithionite followed by complete removal of a...
Figure 7: Structural formulas of iridium and rhodium catalysts (a)–(d) for regeneration of NAD(P)H from NAD(P)...
Figure 8: Two approaches to synthesis of 5′-derivatives of NR+.
Scheme 17: Synthesis of NMN starting from NR+ salt.
Scheme 18: Efficient synthesis of NMN by phosphorylation of 2′,3′-O-isopropylidene-NR+ triflate followed by re...
Scheme 19: Synthesis of a bisphosphonate analogue of β-NAD+ based on DCC-induced conjugation of 2′,3′-O-isopro...
Scheme 20: Synthesis of 5′-acyl and 2′,3′,5′-triacyl derivatives of NR+.
Figure 9: Structural formulas of NMN analogues 39–41.
Scheme 21: Synthesis of 5′-phosphorylated derivatives of NR+ using a “reduction–modification–oxidation” approa...
Scheme 22: Synthesis of 5′-phosphorylated derivatives of NR+ using a “reduction–modification–reoxidation” appr...
Figure 10: Structural formulas of 5′-phosphorylated derivatives of NR+.
Scheme 23: Synthesis of 5′-phosphorylated derivatives of NR+ using a direct NR+ phosphorylation approach.
Figure 11: Structural formulas of amino acid NR+ conjugates.
Scheme 24: Synthesis of amino acid NR+ conjugates using NRH and protected amino acid under CDI-coupling condit...
Figure 12: Chemical structures of known isotopically labelled NR+ analogues and derivatives.
Scheme 25: Synthesis of [2′-3H]-NR+ and [2′-3H]-NMN.
Scheme 26: Synthesis of α- and β-anomers of [1′-2H]-NMN.
Sigmatropic rearrangements of cyclopropenylcarbinol derivatives. Access to diversely substituted alkylidenecyclopropanes
- Guillaume Ernouf,
- Jean-Louis Brayer,
- Christophe Meyer and
- Janine Cossy
Beilstein J. Org. Chem. 2019, 15, 333–350, doi:10.3762/bjoc.15.29
- (TBS) ether of propargyl alcohol by a rhodium-catalyzed cyclopropanation with an aryldiazoacetate followed by reduction of the ester moiety and protecting group manipulation. Phosphinite 6a, generated from alcohol 5a under standard conditions, did not undergo a [2,3]-sigmatropic rearrangement into the
Graphical Abstract
Scheme 1: Representative strategies for the formation of alkylidenecyclopropanes from cyclopropenes and scope...
Scheme 2: [2,3]-Sigmatropic rearrangement of phosphinites 2a–h.
Scheme 3: [2,3]-Sigmatropic rearrangement of a phosphinite derived from enantioenriched cyclopropenylcarbinol...
Scheme 4: Selective reduction of phosphine oxide (E)-3f.
Scheme 5: Attempted thermal [2,3]-sigmatropic rearrangement of phosphinite 6a.
Scheme 6: Computed activation barriers and free enthalpies.
Scheme 7: [2,3]-Sigmatropic rearrangement of phosphinites 6a–j.
Scheme 8: Proposed mechanism for the Lewis base-catalyzed rearrangement of phosphinites 6.
Scheme 9: [3,3]-Sigmatropic rearrangement of tertiary cyclopropenylcarbinyl acetates 10a–c.
Scheme 10: [3,3]-Sigmatropic rearrangement of secondary cyclopropenylcarbinyl esters 10d–h.
Scheme 11: [3,3]-Sigmatropic rearrangement of trichoroacetimidates 12a–i.
Scheme 12: Reaction of trichloroacetamide 13f with pyrrolidine.
Scheme 13: Catalytic hydrogenation of (arylmethylene)cyclopropropane 13f.
Scheme 14: Instability of trichloroacetimidates 21a–c derived from cyclopropenylcarbinols 20a–c.
Scheme 15: [3,3]-Sigmatropic rearrangement of cyanate 27 generated from cyclopropenylcarbinyl carbamate 26.
Scheme 16: Synthesis of alkylidene(aminocyclopropane) derivatives 30–37 from carbamate 26.
Scheme 17: Scope of the dehydration–[3,3]-sigmatropic rearrangement sequence of cyclopropenylcarbinyl carbamat...
Scheme 18: Formation of trifluoroacetamide 50 from carbamate 49.
Scheme 19: Formation of alkylidene[(N-trifluoroacetylamino)cyclopropanes] 51–54.
Scheme 20: Diastereoselective hydrogenation of alkylidenecyclopropane 51.
Scheme 21: Ireland–Claisen rearrangement of cyclopropenylcarbinyl glycolates 56a–l.
Scheme 22: Synthesis and Ireland–Claisen rearrangement of glycolate 61 possessing gem-diester substitution at ...
Scheme 23: Synthesis of alkylidene(gem-difluorocyclopropanes) 66a–h, and 66k–n from propargyl glycolates 64a–n....
Scheme 24: Ireland–Claisen rearrangement of N,N-diBoc glycinates 67a and 67b.
Scheme 25: Diastereoselective hydrogenation of alkylidenecyclopropanes 58a and 74.
Scheme 26: Synthesis of functionalized gem-difluorocyclopropanes 76 and 77 from alkylidenecyclopropane 66a.
Scheme 27: Access to oxa- and azabicyclic compounds 78–80.
Synthesis of 1,2-divinylcyclopropanes by metal-catalyzed cyclopropanation of 1,3-dienes with cyclopropenes as vinyl carbene precursors
- Jesús González,
- Alba de la Fuente,
- María J. González,
- Laura Díez de Tejada,
- Luis A. López and
- Rubén Vicente
Beilstein J. Org. Chem. 2019, 15, 285–290, doi:10.3762/bjoc.15.25
- ) and 3,3-dibenzylcyclopropene (1c). Thus, divinylcyclopropane 3b was obtained in reasonable yields with both catalysts (69% Zn and 75% Rh), albeit better selectivity was obtained again with rhodium(II) catalyst (endo/exo = 17:1). In contrast, the reaction with 1c led to the corresponding cyclopropane
- equimolar mixture of cis/trans diastereoisomers (cis refers to both vinyl substituents). Even though the lack of selectivity was already noticed by Uemura and co-workers in related reactions [17], we attempted the reaction with other zinc salts or rhodium(II) carboxylates as catalysts. Unfortunately, these
- compounds, which led again to oxy-Cope rearranged or [4 + 3]-cycloaddition products using rhodium catalysts [14][28][29][30], or to a C2-allylation of furan with gold catalysts [31]. Finally, to compare the reactivity of cyclopropenes and vinyldiazo compounds, we probed the reaction of 1a with 1,4
Graphical Abstract
Scheme 1: Typical syntheses of 1,2-divinylcyclopropanes and rationale hypothesis for their syntheses from cyc...
Scheme 2: Synthesis of 1,2-divinylcyclopropane 3a: Optimization studies. aIsolated yield. bDetermined by 1H N...
Scheme 3: Synthesis of 1,2-divinylcyclopropanes 3 from cyclopropenes 1 and unbiased 1,3-dienes 2: Scope. (Yie...
Scheme 4: Rh-catalyzed intramolecular cyclopropanation with dienylcyclopropene 4 (the trans/cis ratio is rela...
Scheme 5: Zn- or Rh-catalyzed reactions of cyclopropenes 1 with furan (6) and 1,4-cyclohexadiene (8) and comp...
Oxidative radical ring-opening/cyclization of cyclopropane derivatives
- Yu Liu,
- Qiao-Lin Wang,
- Zan Chen,
- Cong-Shan Zhou,
- Bi-Quan Xiong,
- Pan-Liang Zhang,
- Chang-An Yang and
- Quan Zhou
Beilstein J. Org. Chem. 2019, 15, 256–278, doi:10.3762/bjoc.15.23
- of azide to Rh2(esp)2 complex (bis[rhodium-(α,α,α’,α’-tetramethyl-1,3-benzenedipropionic acid)]) and extrusion of N2. Then, the Rh-nitrene intermediate 65 goes through an intramolecular single electron transfer (SET) to give the nitrogen-centered radical intermediate 66 [87][88][89][90]. Next, the
Graphical Abstract
Scheme 1: The oxidative radical ring-opening/cyclization of cyclopropane derivatives.
Scheme 2: Mn(OAc)3-mediated oxidative radical ring-opening and cyclization of MCPs with malonates.
Scheme 3: Mn(III)-mediated oxidative radical ring-opening and cyclization of MCPs with 1,3-dicarbonyl compoun...
Scheme 4: Heat-promoted ring-opening/cyclization of MCPs with elemental chalgogens.
Scheme 5: Copper(II) acetate-mediated oxidative radical ring-opening and cyclization of MCPs with diphenyl di...
Scheme 6: AIBN-promoted oxidative radical ring-opening and cyclization of MCPs with benzenethiol.
Scheme 7: AIBN-mediated oxidative radical ring-opening and cyclization of MCPs with diethyl phosphites.
Scheme 8: Organic-selenium induced radical ring-opening and cyclization of MCPs derivatives (cyclopropylaldeh...
Scheme 9: Copper(I)-catalyzed oxidative radical trifluoromethylation/ring-opening/cyclization of MCPs with To...
Scheme 10: Ag(I)-mediated trifluoromethylthiolation/ring-opening/cyclization of MCPs with AgSCF3.
Scheme 11: oxidative radical ring-opening and cyclization of MCPs with α-C(sp3)-–H of ethers.
Scheme 12: Oxidative radical ring-opening and cyclization of MCPs with aldehydes.
Scheme 13: Cu(I) or Fe(II)-catalyzed oxidative radical trifluoromethylation/ring-opening/cyclization of MCPs d...
Scheme 14: Rh(II)-catalyzed oxidative radical ring-opening and cyclization of MCPs.
Scheme 15: Ag(I)-catalyzed oxidative radical amination/ring-opening/cyclization of MCPs derivatives.
Scheme 16: Heating-promoted radical ring-opening and cyclization of MCP derivatives (arylvinylidenecyclopropan...
Scheme 17: Bromine radical-mediated ring-opening of alkylidenecyclopropanes.
Scheme 18: Fluoroalkyl (Rf) radical-mediated ring-opening of MCPs.
Scheme 19: Visible-light-induced alkylation/ring-opening/cyclization of cyclopropyl olefins with bromides.
Scheme 20: Mn(III)-mediated ring-opening and [3 + 3]-annulation of cyclopropanols and vinyl azides.
Scheme 21: Ag(I)-catalyzed oxidative ring-opening of cyclopropanols with quinones.
Scheme 22: Ag(I)-catalyzed oxidative ring-opening of cyclopropanols with heteroarenes.
Scheme 23: Cu(I)-catalyzed oxidative ring-opening/trifluoromethylation of cyclopropanols.
Scheme 24: Cu(I)-catalyzed oxidative ring-opening and trifluoromethylation/trifluoromethylthiolation of cyclop...
Scheme 25: Ag(I)-mediated oxidative ring-opening/fluorination of cyclopropanols with Selectfluor.
Scheme 26: Photocatalyzed ring-opening/fluorination of cyclopropanols with Selectfluor.
Scheme 27: Na2S2O8-promoted ring-opening/alkynylation of cyclopropanols with EBX.
Scheme 28: Ag(I)-catalyzed ring-opening and chlorination of cyclopropanols with aldehydes.
Scheme 29: Ag(I)-catalyzed ring-opening/alkynylation of cyclopropanols with EBX.
Scheme 30: Na2S2O8-promoted ring-opening/alkylation of cyclopropanols with acrylamides.
Scheme 31: Cyclopropanol ring-opening initiated tandem cyclization with acrylamides or 2-isocyanobiphenyls.
Scheme 32: Ag(II)-mediated oxidative ring-opening/fluorination of cyclopropanols with AgF2.
Scheme 33: Cu(II)-catalyzed ring-opening/fluoromethylation of cyclopropanols with sulfinate salts.
Scheme 34: Cu(II)-catalyzed ring-opening/sulfonylation of cyclopropanols with sulfinate salts.
Scheme 35: Na2S2O8-promoted ring-opening/arylation of cyclopropanols with propiolamides.
Scheme 36: The ring-opening and [3 + 2]-annulation of cyclopropanols with α,β-unsaturated aldehydes.
Scheme 37: Cu(II)-catalyzed ring-opening/arylation of cyclopropanols with aromatic nitrogen heterocyles.
Scheme 38: Ag(I)-catalyzed ring-opening and difluoromethylthiolation of cyclopropanols with PhSO2SCF2H.
Scheme 39: Ag(I)-catalyzed ring-opening and acylation of cyclopropanols with aldehydes.
Scheme 40: Aerobic oxidation ring-opening of cyclopropanols for the synthesis of 2-oxyranyl ketones.
Scheme 41: Aerobic oxidation ring-opening of cyclopropanols for the synthesis of linear enones.
Scheme 42: Aerobic oxidation ring-opening of cyclopropanols for the synthesis of metabolite.
Gold-catalyzed ethylene cyclopropanation
- Silvia G. Rull,
- Andrea Olmos and
- Pedro J. Pérez
Beilstein J. Org. Chem. 2019, 15, 67–71, doi:10.3762/bjoc.15.7
- copolymerization of ethylene and ethyl diazoacetate with rhodium-based catalysts (Scheme 2a). Ethyl cyclopropanecarboxylate has been prepared in several ways, alternative to the direct carbene addition to ethylene (Scheme 2b): ring contraction of 2-halocyclobutanone [5], cyclization of alkyl 4-halobutanoates [6
- experiments, we tested several group 11 metal-based catalysts that have been described in our group for the catalytic transfer of the CHCO2Et group from ethyl diazoacetate (N2=CHCO2Et, EDA), as well as a rhodium-based catalyst. The experimental procedure started upon placing the catalyst (0.02 mmol) into a
Graphical Abstract
Scheme 1: (a) General metal-catalyzed olefin cyclopropanation reaction with diazo compounds. (b) The ethylene...
Scheme 2: Routes toward ethyl cyclopropanecarboxylate (1). (a) Ethylene cyclopropanation described by De Brui...
Figure 1: Effect of the pressure of ethylene on the yields of ethyl cyclopropanecarboxylate in the reaction o...
Ruthenium-based olefin metathesis catalysts with monodentate unsymmetrical NHC ligands
- Veronica Paradiso,
- Chiara Costabile and
- Fabia Grisi
Beilstein J. Org. Chem. 2018, 14, 3122–3149, doi:10.3762/bjoc.14.292
- to the syn ligand, as suggested by experimental and theoretical studies on the steric and electronic properties of N-cyclohexyl, N’-isopropylphenyl NHC ligands of 191 and 192 evaluated using the corresponding rhodium complexes [60]. A development of this study, which considered the utilization of
Graphical Abstract
Figure 1: Second-generation Grubbs (GII), Hoveyda (HGII), Grela (Gre-II), Blechert (Ble-II) and indenylidene-...
Figure 2: Grubbs (1a) and Hoveyda-type (1b) complexes with N-phenyl, N’-mesityl NHCs.
Figure 3: C–H insertion product 2.
Figure 4: Grubbs (3a–6a) and Hoveyda-type (3b–6b) complexes with N-fluorophenyl, N’-aryl NHCs.
Scheme 1: RCM of diethyl diallylmalonate (7).
Scheme 2: RCM of diethyl allylmethallylmalonate (9).
Scheme 3: RCM of diethyl dimethallylmalonate (11).
Scheme 4: CM of allylbenzene (13) with cis-1,4-diacetoxy-2-butene (14).
Scheme 5: ROMP of 1,5-cyclooctadiene (16).
Figure 5: Grubbs (18a–21a) and Hoveyda-type (18b–21b) catalysts bearing uNHCs with a hexafluoroisopropylalkox...
Figure 6: A Grubbs-type complex with an N-adamantyl, N’-mesityl NHC 22 and the Hoveyda-type complex with a ch...
Figure 7: Grubbs (24a and 25a) and Hoveyda-type (24b and 25b) complexes with N-alkyl, N’-mesityl NHCs.
Figure 8: Grubbs-type complexes 31–34 with N-alkyl, N’-mesityl NHCs.
Figure 9: Grubbs-type complex 35 with an N-cyclohexyl, N’-2,6-diisopropylphenyl NHC.
Figure 10: Hoveyda-type complexes with an N-alkyl, N’-mesityl (36, 37) and an N-alkyl, N’-2,6-diisopropylpheny...
Figure 11: Indenylidene-type complexes 41–43 with N-alkyl, N’-mesityl NHCs.
Figure 12: Grubbs-type complex 44 and its monopyridine derivative 45 containing a chiral uNHC.
Scheme 6: Alternating copolymerization of 46 with 47 and 48.
Figure 13: Pyridine-containing complexes 49–52 and Grubbs-type complex 53.
Figure 14: Hoveyda-type complexes 54–58 in the alternating ROMP of NBE (46) and COE (47).
Figure 15: Catalysts 59 and 60 in the tandem RO–RCM of 47.
Figure 16: Hoveyda-type complexes 61–69 with N-alkyl, N’-aryl NHCs.
Scheme 7: Ethenolysis of methyl oleate (70).
Scheme 8: AROCM of cis-5-norbornene-endo-2,3-dicarboxylic anhydride (75) with styrene.
Figure 17: Hoveyda-type catalysts 79–82 with N-tert-butyl, N’-aryl NHCs.
Scheme 9: Latent ROMP of 83 with catalyst 82.
Figure 18: Indenylidene and Hoveyda-type complexes 85–92 with N-cycloalkyl, N’-mesityl NHCs.
Scheme 10: RCM of N,N-dimethallyl-N-tosylamide (93) with catalyst 85.
Scheme 11: Self metathesis of 13 with catalyst 85.
Figure 19: Grubbs-type complexes 98–104 with N-alkyl, N’-mesityl NHCs.
Figure 20: Grubbs-type complexes 105–115 with N-alkyl, N’-mesityl ligands.
Figure 21: Complexes 116 and 117 bearing a carbohydrate-based NHC.
Figure 22: Complexes 118 and 119 bearing a hemilabile amino-tethered NHC.
Figure 23: Indenylidene-type complexes 120–126 with N-benzyl, N’-mesityl NHCs.
Scheme 12: Diastereoselective ring-rearrangement metathesis (dRRM) of cyclopentene 131.
Figure 24: Indenylidene-type complexes 134 and 135 with N-nitrobenzyl, N’-mesityl NHCs.
Figure 25: Hoveyda-type complexes 136–138 with N-benzyl, N’-mesityl NHCs.
Figure 26: Hoveyda-type complexes 139–142 with N-benzyl, N’-Dipp NHC.
Figure 27: Indenylidene (143–146) and Hoveyda-type (147) complexes with N-heteroarylmethyl, N’-mesityl NHCs.
Figure 28: Hoveyda-type complexes 148 and 149 with N-phenylpyrrole, N’-mesityl NHCs.
Figure 29: Grubbs-type complexes with N-trifluoromethyl benzimidazolidene NHCs 150–153, 155 and N-isopropyl be...
Scheme 13: Ethenolysis of ethyl oleate 156.
Scheme 14: Ethenolysis of cis-cyclooctene (47).
Figure 30: Grubbs-type C1-symmetric (164) and C2-symmetric (165) catalysts with a backbone-substituted NHC.
Figure 31: Possible syn and anti rotational isomers of catalyst 164.
Scheme 15: ARCM of substrates 166, 168 and 170.
Figure 32: Hoveyda (172) and Grubbs-type (173,174) backbone-substituted C1-symmetric NHC complexes.
Scheme 16: ARCM of 175,177 and 179 with catalyst 174.
Figure 33: Grubbs-type C1-symmetric NHC catalysts bearing N-propyl (181, 182) or N-benzyl (183, 184) groups on...
Scheme 17: ARCM of 185 and 187 promoted by 184 to form the encumbered alkenes 186 and 188.
Figure 34: N-Alkyl, N’-isopropylphenyl NHC ruthenium complexes with syn (189, 191) and anti (190, 192) phenyl ...
Figure 35: Hoveyda-type complexes 193–198 bearing N-alkyl, N’-aryl backbone-substituted NHC ligands.
Scheme 18: ARCM of 166 and 199 promoted by 192b.
Figure 36: Enantiopure catalysts 201a and 201b with syn phenyl units on the NHC backbone.
Figure 37: Backbone-monosubstituted catalysts 202–204.
Figure 38: Grubbs (205a) and Hoveyda-type (205b) backbone-monosubstituted catalysts.
Scheme 19: AROCM of 206 with allyltrimethylsilane promoted by catalyst 205a.
Stereodivergent approach in the protected glycal synthesis of L-vancosamine, L-saccharosamine, L-daunosamine and L-ristosamine involving a ring-closing metathesis step
- Pierre-Antoine Nocquet,
- Aurélie Macé,
- Frédéric Legros,
- Jacques Lebreton,
- Gilles Dujardin,
- Sylvain Collet,
- Arnaud Martel,
- Bertrand Carboni and
- François Carreaux
Beilstein J. Org. Chem. 2018, 14, 2949–2955, doi:10.3762/bjoc.14.274
- introduction of nitrogen in the convenient position (C3) could be performed by a stereopecific nitrene insertion reaction catalyzed by rhodium(II) complexes [24][25]. Herein, we describe our outcomes related to the implementation of this strategy for the synthesis of L-vancosamine derivative 1, as well as its
- data [9]. As an example, the expected protected glycal of L-daunosamine 3 [9][47] was obtained by regioselective rhodium nitrene insertion thus demonstrating the usefulness of this strategy for the synthesis of such compounds. Conclusion We developed an alternative route to 3-aminoglycals through ring
Graphical Abstract
Figure 1: N,N-Dimethyl-L-vancosamine as substructure of kidamycin and pluramycin.
Figure 2: Glycals as relevant scaffolds for constructing aryl C-glycosidic linkage.
Figure 3: Strategy including a ring-closing metathesis of vinyl ethers as key step for the preparation of sev...
Scheme 1: Evans aldol reaction for the preparation of diastereomeric compounds 13a and 13b.
Scheme 2: Alternative preparation of 13b based on a diastereoselective allylboration.
Scheme 3: O-Vinylation-ring-closing metathesis sequence for access to 3-amino glycals.
Scheme 4: Synthesis of key intermediate 23 for the C-3 unbranched amino glycals preparation.
Scheme 5: Access to diastereoisomeric compounds 3 and 4 from 23.
