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Search for "transition-metal-catalyzed" in Full Text gives 247 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.
Three-component reactions of aromatic amines, 1,3-dicarbonyl compounds, and α-bromoacetaldehyde acetal to access N-(hetero)aryl-4,5-unsubstituted pyrroles
- Wenbo Huang,
- Kaimei Wang,
- Ping Liu,
- Minghao Li,
- Shaoyong Ke and
- Yanlong Gu
Beilstein J. Org. Chem. 2020, 16, 2920–2928, doi:10.3762/bjoc.16.241
- pyrrole syntheses [9][10][11], which have been developed to harvest the pyrrole frameworks. In the past few years, the interest in developing new methods to synthesize this heterocyclic motif has rapidly grown; transition metal-catalyzed cyclization [12][13][14] and multicomponent reactions [15][16][17
Graphical Abstract
Figure 1: Representative biologically active N-(hetero)aryl-4,5-unsubstituted pyrrole scaffolds.
Scheme 1: Typical routes to N-(heteroaryl)-4,5-unsubstituted pyrroles.
Scheme 2: Substrate scope of the pyrrole synthesis.
Scheme 3: Synthesis of N-heterocyclic pyrroles.
Scheme 4: Direct synthesis of pyrrole-3-carboxamide derivatives.
Scheme 5: Plausible mechanism of the three-component reaction.
Scheme 6: Synthesis of polysubstituted pyrazolo[3,4-b]pyridine derivatives.
Regioselective cobalt(II)-catalyzed [2 + 3] cycloaddition reaction of fluoroalkylated alkynes with 2-formylphenylboronic acids: easy access to 2-fluoroalkylated indenols
- Tatsuya Kumon,
- Miroku Shimada,
- Jianyan Wu,
- Shigeyuki Yamada and
- Tsutomu Konno
Beilstein J. Org. Chem. 2020, 16, 2193–2200, doi:10.3762/bjoc.16.184
- best of our knowledge, there are no reports on the practical synthesis of disubstituted 2-fluoroalkylated indenols so far. Transition-metal-catalyzed carbocyclization reactions of alkynes with benzene derivatives having a leaving group X (X = Br, I, OTs, B(OH)2) have been widely considered as one of
Graphical Abstract
Figure 1: Indenol skeleton.
Scheme 1: Synthesis of 2,3-disubstituted indene derivatives.
Scheme 2: Cobalt-catalyzed [2 + 3] cycloaddition reaction of the fluorinated alkynes 1 with various 2-formylp...
Scheme 3: Synthesis of the fluoroalkylated indenone 6 and the indanone 7 from the indenol 3aA. The yields wer...
Scheme 4: Stereochemical assignment of 5aA and 7 based on NMR techniques. The cross-peaks were observed throu...
Scheme 5: Proposed reaction mechanism.
Efficient [(NHC)Au(NTf2)]-catalyzed hydrohydrazidation of terminal and internal alkynes
- Maximillian Heidrich and
- Herbert Plenio
Beilstein J. Org. Chem. 2020, 16, 2080–2086, doi:10.3762/bjoc.16.175
- addition product were obtained. We recently reported the excellent activity of the very bulky bispentiptycenyl-substituted (NHC)Au complexes in the hydration of terminal and internal alkynes [43] as well as in other transition-metal-catalyzed transformations [44][45]. We were now interested, whether
Graphical Abstract
Scheme 1: Simplified mechanism of the hydrohydrazidation (NuH= ArCONHNH2) of alkynes.
Scheme 2: [(NHC)Au(NTf2)] complexes tested in hydrohydrazidation reactions of phenylacetylene.
Scheme 3: Hydrohydrazidation of terminal alkynes in chlorobenzene and anisole using complex 1 (first line sol...
Scheme 4: Hydrohydrazidation of internal alkynes in chlorobenzene and anisole using complex 1. Reaction tempe...
Metal-free synthesis of phosphinoylchroman-4-ones via a radical phosphinoylation–cyclization cascade mediated by K2S2O8
- Qiang Liu,
- Weibang Lu,
- Guanqun Xie and
- Xiaoxia Wang
Beilstein J. Org. Chem. 2020, 16, 1974–1982, doi:10.3762/bjoc.16.164
- appropriate radical precursors through visible-light promoted systems [15][16], transition-metal-catalyzed systems [17][18], or transition-metal-free systems [19][20], have emerged as a powerful strategy for the synthesis of diversely functionalized chroman-4-one derivatives. Organophosphorus compounds are
Graphical Abstract
Figure 1: Biologically active compounds featuring the chroman-4-one framework.
Scheme 1: Methods to produce phosphonate-substituted chroman-4-ones.
Figure 2: X-ray structure of compound 3aa (CCDC 2002878).
Scheme 2: Scope of 2-(allyloxy)arylaldehydes. Reaction conditions: 1 (0.3 mmol, 1 equiv), 2a (1.5 equiv) [2f ...
Scheme 3: Scope of diphenylphosphine oxides. Reaction conditions: 1a (0.3 mmol, 1 equiv), 2 (1.5 equiv), DMSO...
Scheme 4: Gram-scale reaction.
Scheme 5: Control experiments and proposed mechanism.
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
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.
Tuneable access to indole, indolone, and cinnoline derivatives from a common 1,4-diketone Michael acceptor
- Dalel El-Marrouki,
- Sabrina Touchet,
- Abderrahmen Abdelli,
- Hédi M’Rabet,
- Mohamed Lotfi Efrit and
- Philippe C. Gros
Beilstein J. Org. Chem. 2020, 16, 1722–1731, doi:10.3762/bjoc.16.144
- ][38][39] or triketones [10][13] and enaminones [40][41][42][43] as starting materials. For the synthesis of cinnoline derivatives, aryldiazenes and aryltriazenes are substrates of choice for transition-metal-catalyzed (Rh, Pd, Cu) cross-coupling reactions, followed by intramolecular cyclizations [44
Graphical Abstract
Figure 1: Examples of bioactive nitrogen-containing heterocycles (indole [9], indolone [10], and cinnoline [11] derivati...
Scheme 1: General strategy to access indole, indolone, and cinnoline derivatives from 1,4-diketones.
Scheme 2: Synthesis of the 1,4-diketones 5a–k via the Nef reaction or the Wittig reaction. i) HCHO (aq), DMAP...
Scheme 3: Mechanism of the formation of indole and indolone derivatives.
Scheme 4: Synthesis of the indoles 6a–f and the corresponding side product indolones 7a–f.
Scheme 5: Reaction of 5b with a diamine.
Scheme 6: Synthesis of the indoles 6h–l.
Scheme 7: Synthesis of the indolone derivatives 7b, 7d, and 7g–k.
Scheme 8: Synthesis of the cinnoline derivatives 8a–k.
Scheme 9: Proposed mechanism for the preparation of the compounds 6, 7, and 8.
Photocatalyzed syntheses of phenanthrenes and their aza-analogues. A review
- Alessandra Del Tito,
- Havall Othman Abdulla,
- Davide Ravelli,
- Stefano Protti and
- Maurizio Fagnoni
Beilstein J. Org. Chem. 2020, 16, 1476–1488, doi:10.3762/bjoc.16.123
- the design of dye-sensitized solar cells (DSSC) [4]. Typical methods for the construction of a phenanthrene core involve transition-metal-catalyzed cycloisomerizations starting from arynes [5][6], o-alkynyl-biaryls [7][8], or substituted N-tosylhydrazones [9]. However, since the introduction in 1964
- , among the others, the anionic ring-closure of 2-cyanobiaryls by using organometallic reagents [19][20], and an impressive number of transition-metal-catalyzed C(sp2)–C(sp2) cross-coupling processes [21][22][23]. In the last decade, however, photochemical reactions, especially those promoted by a
Graphical Abstract
Figure 1: Bioactive phenanthridine and phenanthridinium derivatives.
Scheme 1: Synthesis of phenanthrenes by a photo-Pschorr reaction.
Scheme 2: Synthesis of phenanthrenes by a benzannulation reaction.
Scheme 3: Photocatalytic cyclization of α-bromochalcones for the synthesis of phenanthrenes.
Figure 2: Carbon-centered and nitrogen-centered radicals used for the synthesis of phenanthridines.
Scheme 4: General scheme describing the synthesis of phenanthridines from isocyanides via imidoyl radicals.
Scheme 5: Synthesis of substituted phenanthridines involving the intermediacy of electrophilic radicals.
Scheme 6: Photocatalyzed synthesis of 6-β-ketoalkyl phenanthridines.
Scheme 7: Synthesis of 6-substituted phenanthridines through the addition of trifluoromethyl (path a), phenyl...
Scheme 8: Synthesis of 6-(trifluoromethyl)-7,8-dihydrobenzo[k]phenanthridine.
Scheme 9: Phenanthridine syntheses by using photogenerated radicals formed through a C–H bond homolytic cleav...
Scheme 10: Trifluoroacetimidoyl chlorides as starting substrates for the synthesis of 6-(trifluoromethyl)phena...
Scheme 11: Synthesis of phenanthridines via aryl–aryl-bond formation.
Scheme 12: Oxidative conversion of N-biarylglycine esters to phenanthridine-6-carboxylates.
Scheme 13: Photocatalytic synthesis of benzo[f]quinolines from 2-heteroaryl-substituted anilines and heteroary...
Scheme 14: Synthesis of noravicine (14.2a) and nornitidine (14.2b) alkaloids.
Scheme 15: Gram-scale synthesis of the alkaloid trisphaeridine (15.3).
Scheme 16: Synthesis of phenanthridines starting from vinyl azides.
Scheme 17: Synthesis of pyrido[4,3,2-gh]phenanthridines 17.5a–d through the radical trifluoromethylthiolation ...
Scheme 18: The direct oxidative C–H amidation involving amidyl radicals for the synthesis of phenanthridones.
One-pot synthesis of 1,3,5-triazine-2,4-dithione derivatives via three-component reactions
- Gui-Feng Kang and
- Gang Zhang
Beilstein J. Org. Chem. 2020, 16, 1447–1455, doi:10.3762/bjoc.16.120
- with the reaction conditions and yielded the corresponding products (6oa–va, 48–92%), allowing for further functionalization through subsequent transition-metal-catalyzed coupling reactions. Intriguingly, it was found that compounds with bicycloaryl and heteroaryl ring systems were also viable
Graphical Abstract
Figure 1: Selected examples of triazinethione-containing bioactive compounds.
Scheme 1: Strategies for the synthesis of triazinethiones.
Scheme 2: Aldehyde substrate scope of three-component reaction of aldehydes, thiourea and trimethyl orthoform...
Scheme 3: Orthoformate substrate scope of the three component reaction of benzaldehyde, thiourea, and orthofo...
Scheme 4: Gram-scale synthesis of 6aa.
Figure 2: X-ray structure of 6-(methylthio)-4-phenyl-3,4-dihydro-1,3,5-triazine-2(1H)-thione (6aa) with therm...
Scheme 5: Control experiments for investigation of the mechanism.
Scheme 6: Plausible mechanism.
Fluorinated phenylalanines: synthesis and pharmaceutical applications
- Laila F. Awad and
- Mohammed Salah Ayoup
Beilstein J. Org. Chem. 2020, 16, 1022–1050, doi:10.3762/bjoc.16.91
- the corresponding (R)-N-acetyl ester 60 with >99.5% ee [50] (Scheme 13). The synthesis of 3-bromo-4-fluoro-(S)-Phe (65) was carried out by reacting 3-bromo-4-fluorobenzaldehyde (61) and N-acetylglycine (51a) to provide intermediate 63 in high yield and without purification. Then, the transition-metal
- -catalyzed asymmetric hydrogenation of the α-amidocinnamic acid 63 using the less frequently used ferrocene-based ligand Me-BoPhoz led to the N-acetyl-ʟ-phenylalanine derivative 64 with complete conversion and with 94% ee. The desired enantiomer (S)-65 was obtained as a single isomer (>99% ee) after
Graphical Abstract
Figure 1: Categories I–V of fluorinated phenylalanines.
Scheme 1: Synthesis of fluorinated phenylalanines via Jackson’s method.
Scheme 2: Synthesis of all-cis-tetrafluorocyclohexylphenylalanines.
Scheme 3: Synthesis of ʟ-4-[sulfono(difluoromethyl)]phenylalanine (nPt: neopentyl, TCE: trichloroethyl).
Scheme 4: Synthesis of ʟ-4-[sulfono(difluoromethyl)]phenylalanine derivatives 17.
Scheme 5: Synthesis of fluorinated Phe analogues from Cbz-protected aminomalonates.
Scheme 6: Synthesis of tetrafluorophenylalanine analogues via the 3-methyl-4-imidazolidinone auxiliary 25.
Scheme 7: Synthesis of tetrafluoro-Phe derivatives via chiral auxiliary 31.
Scheme 8: Synthesis of 2,5-difluoro-Phe and 2,4,5-trifluoro-Phe via Schöllkopf reagent 34.
Scheme 9: Synthesis of 2-fluoro- and 2,6-difluoro Fmoc-Phe derivatives starting from chiral auxiliary 39.
Scheme 10: Synthesis of 2-[18F]FPhe via chiral auxiliary 43.
Scheme 11: Synthesis of FPhe 49a via photooxidative cyanation.
Scheme 12: Synthesis of FPhe derivatives via Erlenmeyer azalactone synthesis.
Scheme 13: Synthesis of (R)- and (S)-2,5-difluoro Phe via the azalactone method.
Scheme 14: Synthesis of 3-bromo-4-fluoro-(S)-Phe (65).
Scheme 15: Synthesis of [18F]FPhe via radiofluorination of phenylalanine with [18F]F2 or [18F]AcOF.
Scheme 16: Synthesis of 4-borono-2-[18F]FPhe.
Scheme 17: Synthesis of protected 4-[18F]FPhe via arylstannane derivatives.
Scheme 18: Synthesis of FPhe derivatives via intermediate imine formation.
Scheme 19: Synthesis of FPhe derivatives via Knoevenagel condensation.
Scheme 20: Synthesis of FPhe derivatives 88a,b from aspartic acid derivatives.
Scheme 21: Synthesis of 2-(2-fluoroethyl)phenylalanine derivatives 93 and 95.
Scheme 22: Synthesis of FPhe derivatives via Zn2+ complexes.
Scheme 23: Synthesis of FPhe derivatives via Ni2+ complexes.
Scheme 24: Synthesis of 3,4,5-trifluorophenylalanine hydrochloride (109).
Scheme 25: Synthesis of FPhe derivatives via phenylalanine aminomutase (PAM).
Scheme 26: Synthesis of (R)-2,5-difluorophenylalanine 115.
Scheme 27: Synthesis of β-fluorophenylalanine via 2-amino-1,3-diol derivatives.
Scheme 28: Synthesis of β-fluorophenylalanine derivatives via the oxazolidinone chiral auxiliary 122.
Scheme 29: Synthesis of β-fluorophenylalanine from pyruvate hemiketal 130.
Scheme 30: Synthesis of β-fluorophenylalanine (136) via fluorination of β-hydroxyphenylalanine (137).
Scheme 31: Synthesis of β-fluorophenylalanine from aziridine derivatives.
Scheme 32: Synthesis of β-fluorophenylalanine 136 via direct fluorination of pyruvate esters.
Scheme 33: Synthesis of β-fluorophenylalanine via fluorination of ethyl 3-phenylpyruvate enol using DAST.
Scheme 34: Synthesis of β-fluorophenylalanine derivatives using photosensitizer TCB.
Scheme 35: Synthesis of β-fluorophenylalanine derivatives using Selectflour and dibenzosuberenone.
Scheme 36: Synthesis of protected β-fluorophenylalanine via aziridinium intermediate 150.
Scheme 37: Synthesis of β-fluorophenylalanine derivatives via fluorination of α-hydroxy-β-aminophenylalanine d...
Scheme 38: Synthesis of β-fluorophenylalanine derivatives from α- or β-hydroxy esters 152a and 155.
Scheme 39: Synthesis of a series of β-fluoro-Phe derivatives via Pd-catalyzed direct fluorination of β-methyle...
Scheme 40: Synthesis of series of β-fluorinated Phe derivatives using quinoline-based ligand 162 in the Pd-cat...
Scheme 41: Synthesis of β,β-difluorophenylalanine derivatives from 2,2-difluoroacetaldehyde derivatives 164a,b....
Scheme 42: Synthesis of β,β-difluorophenylalanine derivatives via an imine chiral auxiliary.
Scheme 43: Synthesis of α-fluorophenylalanine derivatives via direct fluorination of protected Phe 174.
Figure 2: Structures of PET radiotracers of 18FPhe derivatives.
Figure 3: Structures of melfufen (179) and melphalan (180) anticancer drugs.
Figure 4: Structure of gastrazole (JB95008, 181), a CCK2 receptor antagonist.
Figure 5: Dual CCK1/CCK2 antagonist 182.
Figure 6: Structure of sitagliptin (183), an antidiabetic drug.
Figure 7: Structure of retaglpitin (184) and antidiabetic drug.
Figure 8: Structure of evogliptin (185), an antidiabetic drug.
Figure 9: Structure of LY2497282 (186) a DPP-4 inhibitor for the treatment of type II diabetes.
Figure 10: Structure of ulimorelin (187).
Figure 11: Structure of GLP1R (188).
Figure 12: Structures of Nav1.7 blockers 189 and 190.
Preparation of 2-phospholene oxides by the isomerization of 3-phospholene oxides
- Péter Bagi,
- Réka Herbay,
- Nikolett Péczka,
- Zoltán Mucsi,
- István Timári and
- György Keglevich
Beilstein J. Org. Chem. 2020, 16, 818–832, doi:10.3762/bjoc.16.75
- ][4]. A heterocyclic ring containing a P atom appears in many popular P(III)-ligands, such as BPE, DuPhos, TangPhos, DuanPhos, ZhangPhos [5][6][7][8][9][10][11], among which a number of species may be considered as privileged ligands for transition metal-catalyzed enantioselective transformations [12
Graphical Abstract
Figure 1: Examples for catalytically or biologically active molecules containing five-membered P-heterocyclic...
Scheme 1: Comparison of the isomerization of 1-phenyl-3-phospholene oxide (5), 1-phenyl-3-methyl-3-phospholen...
Scheme 2: Three possible reaction mechanisms considered in the theoretical studies for the isomerization of 3...
Figure 2: The full time experimental kinetic curves (a); The initial part of the kinetic curves of 1c–f and 1h...
Scheme 3: Computed reaction mechanism of the 3-phospholene oxide (1) 2-phospholene oxide (4) isomerization un...
Scheme 4: Computed reaction mechanism of the 3-phospholene oxide (1) 2-phospholene oxide (4) isomerization un...
Combining enyne metathesis with long-established organic transformations: a powerful strategy for the sustainable synthesis of bioactive molecules
- Valerian Dragutan,
- Ileana Dragutan,
- Albert Demonceau and
- Lionel Delaude
Beilstein J. Org. Chem. 2020, 16, 738–755, doi:10.3762/bjoc.16.68
- -metal-catalyzed transformations were needed to achieve the total synthesis of des-epoxy-amphidinolide N, including a palladium asymmetric allylic alkylation (Pd-AAA), a Mukaiyama aldol reaction (with Sn), and a Krische allylation (with Ir) [72]. As special feature of this procedure, an Evans aldol
- metathesis between the formed propargylic derivative and an appropriate allylic alcohol promoted by the Grubbs second-generation catalyst, finally produced in high yield (85%) the intermediate diene 6, as an essential building block for the southern fragment (Scheme 9). Several other asymmetric transition
Graphical Abstract
Scheme 1: Intramolecular (A) and intermolecular (B) enyne metathesis reactions.
Scheme 2: Ene–yne and yne–ene mechanisms for intramolecular enyne metathesis reactions.
Scheme 3: Metallacarbene mechanism in intermolecular enyne metathesis.
Scheme 4: The Oguri strategy for accessing artemisinin analogs 1a–c through enyne metathesis.
Scheme 5: Access to the tetracyclic core of nanolobatolide (2) via tandem enyne metathesis followed by an Eu(...
Scheme 6: Synthesis of (−)-amphidinolide E (3) using an intermolecular enyne metathesis as the key step.
Scheme 7: Synthesis of amphidinolide K (4) by an enyne metathesis route.
Scheme 8: Trost synthesis of des-epoxy-amphidinolide N (5) [72].
Scheme 9: Enyne metathesis between the propargylic derivative and the allylic alcohol in the synthesis of the...
Scheme 10: Synthetic route to amphidinolide N (6a).
Scheme 11: Synthesis of the stereoisomeric precursors of amphidinolide V (7a and 7b) through alkyne ring-closi...
Scheme 12: Synthesis of the anthramycin precursor 8 from ʟ-methionine by a tandem enyne metathesis–cross metat...
Scheme 13: Synthesis of (−)‐clavukerin A (9) and (−)‐isoclavukerin A (10) by an enyne metathesis route startin...
Scheme 14: Synthesis of (−)-isoguaiene (11) through an enyne metathesis as the key step.
Scheme 15: Synthesis of erogorgiaene (12) by a tandem enyne metathesis/cross metathesis sequence using the sec...
Scheme 16: Synthesis of (−)-galanthamine (13) from isovanilin by an enyne metathesis.
Scheme 17: Application of enyne metathesis for the synthesis of kempene diterpenes 14a–c.
Scheme 18: Synthesis of the alkaloid (+)-lycoflexine (15) through enyne metathesis.
Scheme 19: Synthesis of the AB subunits of manzamine A (16a) and E (16b) by enyne metathesis.
Scheme 20: Jung's synthesis of rhodexin A (17) by enyne metathesis/cross metathesis reactions.
Scheme 21: Total synthesis of (−)-flueggine A (18) and (+)-virosaine B (19) from Weinreb amide by enyne metath...
Scheme 22: Access to virgidivarine (20) and virgiboidine (21) by an enyne metathesis route.
Scheme 23: Enyne metathesis approach to (−)-zenkequinone B (22).
Scheme 24: Access to C-aryl glycoside 23 by an intermolecular enyne metathesis/Diels–Alder cycloaddition.
Scheme 25: Synthesis of spiro-C-aryl glycoside 24 by a tandem intramolecular enyne metathesis/Diels–Alder reac...
Scheme 26: Pathways to (−)-exiguolide (25) by Trost’s Ru-catalyzed enyne cross-coupling and cross-metathesis [94].
Recent advances in Cu-catalyzed C(sp3)–Si and C(sp3)–B bond formation
- Balaram S. Takale,
- Ruchita R. Thakore,
- Elham Etemadi-Davan and
- Bruce H. Lipshutz
Beilstein J. Org. Chem. 2020, 16, 691–737, doi:10.3762/bjoc.16.67
- reactions are discussed. Keywords: C–B bonds; copper catalysis; C–Si bonds; enantioselective reactions; sp3 carbon functionalization; Introduction Transition-metal-catalyzed silylation and borylation are useful transformations [1], widely studied because organosilicon [2][3] and organoboron compounds [4
Graphical Abstract
Scheme 1: Pharmaceuticals possessing a silicon or boron atom.
Scheme 2: The first Cu-catalyzed C(sp3)–Si bond formation.
Scheme 3: Conversion of benzylic phosphate 6 to the corresponding silane.
Scheme 4: Conversion of alkyl triflates to alkylsilanes.
Scheme 5: Conversion of secondary alkyl triflates to alkylsilanes.
Scheme 6: Conversion of alkyl iodides to alkylsilanes.
Scheme 7: Trapping of intermediate radical through cascade reaction.
Scheme 8: Radical pathway for conversion of alkyl iodides to alkylsilanes.
Scheme 9: Conversion of alkyl ester of N-hydroxyphthalimide to alkylsilanes.
Scheme 10: Conversion of gem-dibromides to bis-silylalkanes.
Scheme 11: Conversion of imines to α-silylated amines (A) and the reaction pathway (B).
Scheme 12: Conversion of N-tosylimines to α-silylated amines.
Scheme 13: Screening of diamine ligands.
Scheme 14: Conversion of N-tert-butylsulfonylimines to α-silylated amines.
Scheme 15: Conversion of aldimines to nonracemic α-silylated amines.
Scheme 16: Conversion of N-tosylimines to α-silylated amines.
Scheme 17: Reaction pathway [A] and conversion of aldehydes to α-silylated alcohols [B].
Scheme 18: Conversion of aldehydes to benzhydryl silyl ethers.
Scheme 19: Conversion of ketones to 1,2-diols (A) and conversion of imines to 1,2-amino alcohols (B).
Scheme 20: Ligand screening (A) and conversion of aldehydes to α-silylated alcohols (B).
Scheme 21: Conversion of aldehydes to α-silylated alcohols.
Scheme 22: 1,4-Additions to α,β-unsaturated ketones.
Scheme 23: 1,4-Additions to unsaturated ketones to give β-silylated derivatives.
Scheme 24: Additions onto α,β-unsaturated lactones to give β-silylated lactones.
Scheme 25: Conversion of α,β-unsaturated to β-silylated lactams.
Scheme 26: Conversion of N-arylacrylamides to silylated oxindoles.
Scheme 27: Conversion of α,β-unsaturated carbonyl compounds to silylated tert-butylperoxides.
Scheme 28: Catalytic cycle for Cu(I) catalyzed α,β-unsaturated compounds.
Scheme 29: Conversion of p-quinone methides to benzylic silanes.
Scheme 30: Conversion of α,β-unsaturated ketimines to regio- and stereocontrolled allylic silanes.
Scheme 31: Conversion of α,β-unsaturated ketimines to enantioenriched allylic silanes.
Scheme 32: Regioselective conversion of dienedioates to allylic silanes.
Scheme 33: Conversion of alkenyl-substituted azaarenes to β-silylated adducts.
Scheme 34: Conversion of conjugated benzoxazoles to enantioenriched β-silylated adducts.
Scheme 35: Conversion of α,β-unsaturated carbonyl indoles to α-silylated N-alkylated indoles.
Scheme 36: Conversion of β-amidoacrylates to α-aminosilanes.
Scheme 37: Conversion of α,β-unsaturated ketones to enantioenriched β-silylated ketones, nitriles, and nitro d...
Scheme 38: Regio-divergent silacarboxylation of allenes.
Scheme 39: Silylation of diazocarbonyl compounds, (A) asymmetric and (B) racemic.
Scheme 40: Enantioselective hydrosilylation of alkenes.
Scheme 41: Conversion of 3-acylindoles to indolino-silanes.
Scheme 42: Proposed mechanism for the silylation of 3-acylindoles.
Scheme 43: Silyation of N-chlorosulfonamides.
Scheme 44: Conversion of acyl silanes to α-silyl alcohols.
Scheme 45: Conversion of N-tosylaziridines to β-silylated N-tosylamines.
Scheme 46: Conversion of N-tosylaziridines to silylated N-tosylamines.
Scheme 47: Conversion of 3,3-disubstituted cyclopropenes to silylated cyclopropanes.
Scheme 48: Conversion of conjugated enynes to 1,3-bis(silyl)propenes.
Scheme 49: Proposed sequence for the Cu-catalyzed borylation of substituted alkenes.
Scheme 50: Cu-catalyzed synthesis of nonracemic allylic boronates.
Scheme 51: Cu–NHC catalyzed synthesis of α-substituted allylboronates.
Scheme 52: Synthesis of α-chiral (γ-alkoxyallyl)boronates.
Scheme 53: Cu-mediated formation of nonracemic cis- or trans- 2-substituted cyclopropylboronates.
Scheme 54: Cu-catalyzed synthesis of γ,γ-gem-difluoroallylboronates.
Scheme 55: Cu-catalyzed hydrofunctionalization of internal alkenes and vinylarenes.
Scheme 56: Cu-catalyzed Markovnikov and anti-Markovnikov borylation of alkenes.
Scheme 57: Cu-catalyzed borylation/ortho-cyanation/Cope rearrangement.
Scheme 58: Borylfluoromethylation of alkenes.
Scheme 59: Cu-catalyzed synthesis of tertiary nonracemic alcohols.
Scheme 60: Synthesis of densely functionalized and synthetically versatile 1,2- or 4,3-borocyanated 1,3-butadi...
Scheme 61: Cu-catalyzed trifunctionalization of allenes.
Scheme 62: Cu-catalyzed selective arylborylation of arenes.
Scheme 63: Asymmetric borylative coupling between styrenes and imines.
Scheme 64: Regio-divergent aminoboration of unactivated terminal alkenes.
Scheme 65: Cu-catalyzed 1,4-borylation of α,β-unsaturated ketones.
Scheme 66: Cu-catalyzed protodeboronation of α,β-unsaturated ketones.
Scheme 67: Cu-catalyzed β-borylation of α,β-unsaturated imines.
Scheme 68: Cu-catalyzed synthesis of β-trifluoroborato carbonyl compounds.
Scheme 69: Asymmetric 1,4-borylation of α,β-unsaturated carbonyl compounds.
Scheme 70: Cu-catalyzed ACB and ACA reactions of α,β-unsaturated 2-acyl-N-methylimidazoles.
Scheme 71: Cu-catalyzed diborylation of aldehydes.
Scheme 72: Umpolung pathway for chiral, nonracemic tertiary alcohol synthesis (top) and proposed mechanism for...
Scheme 73: Cu-catalyzed synthesis of α-hydroxyboronates.
Scheme 74: Cu-catalyzed borylation of ketones.
Scheme 75: Cu-catalyzed borylation of unactivated alkyl halides.
Scheme 76: Cu-catalyzed borylation of allylic difluorides.
Scheme 77: Cu-catalyzed borylation of cyclic and acyclic alkyl halides.
Scheme 78: Cu-catalyzed borylation of unactivated alkyl chlorides and bromides.
Scheme 79: Cu-catalyzed decarboxylative borylation of carboxylic acids.
Scheme 80: Cu-catalyzed borylation of benzylic, allylic, and propargylic alcohols.
Efficient synthesis of 3,6,13,16-tetrasubstituted-tetrabenzo[a,d,j,m]coronenes by selective C–H/C–O arylations of anthraquinone derivatives
- Seiya Terai,
- Yuki Sato,
- Takuya Kochi and
- Fumitoshi Kakiuchi
Beilstein J. Org. Chem. 2020, 16, 544–550, doi:10.3762/bjoc.16.51
- groups to form biaryl frameworks. Traditionally, transition-metal-catalyzed cross-coupling reactions of aryl halides or pseudohalides with arylmetal reagents have been employed for the connection of two aryl units [5][6][7][8][9]. However, in search of more efficient synthetic routes, C–H arylation
Graphical Abstract
Scheme 1: Projected synthetic routes for 3,6,13,16-tetrasubstituted tetrabenzo[a,d,j,m]coronenes.
Scheme 2: Reported syntheses of 2,7,12,17-tetrasubstituted tetrabenzo[a,d,j,m]coronenes.
Scheme 3: C–H tetraarylation of anthraquinone (1).
Scheme 4: C–H diarylation of 1,4-diarylanthraquinones 5.
Figure 1: Normalized UV–vis absorption spectra of 7aa, 7bb, and 7ba.
Figure 2: Effects of the concentration and the temperature on the 1H NMR spectra of 7aa.
Copper-catalyzed remote C–H arylation of polycyclic aromatic hydrocarbons (PAHs)
- Anping Luo,
- Min Zhang,
- Zhangyi Fu,
- Jingbo Lan,
- Di Wu and
- Jingsong You
Beilstein J. Org. Chem. 2020, 16, 530–536, doi:10.3762/bjoc.16.49
- molecules, thus having drawn much attention. Transition metal-catalyzed C–X/C–M cross-coupling reactions such as Suzuki and Stille couplings are the main approaches to achieve the arylation of PAHs [7][8][9][10][11]. However, the selective arylation of the C7-position of 1-naphthoic acid derivatives remains
- a challenging task due to the inaccessibility of the corresponding 7-halonaphthalene substrates [12]. Recently, transition metal-catalyzed C–H bond functionalization has emerged as a powerful tool to construct various biaryl skeletons [13][14][15][16][17]. The direct C7−H arylation of 1-naphthoic
- acid derivatives is undoubtedly a more effective route for the synthesis of 7-arylnaphthalene derivatives. Although the transition metal-catalyzed C2−H and C8−H arylations of 1-naphthoic acid derivatives have been widely reported, the studies on their C7−H arylation remain rare [18][19][20][21][22][23
Graphical Abstract
Scheme 1: Direct C–H arylation of PAHs.
Scheme 2: Scope of aryliodonium salts. Reaction conditions: 1a (0.2 mmol), 2 (0.3 mmol) in DCE (1 mL) at 70 °...
Scheme 3: Scope of PAHs. Reaction conditions: 1 (0.2 mmol), 2a (0.3 mmol) in DCE (1 mL) at 70 °C under N2 for...
Scheme 4: Proposed catalytic cycle.
Figure 1: a) UV-visible absorption spectra of 4k, 4n and 4o in toluene (1 × 10−5 mol/L). b) Emission spectra ...
Room-temperature Pd/Ag direct arylation enabled by a radical pathway
- Amy L. Mayhugh and
- Christine K. Luscombe
Beilstein J. Org. Chem. 2020, 16, 384–390, doi:10.3762/bjoc.16.36
- . There are limited examples across the aryl C–H functionalization literature indicating a transition metal-catalyzed radical process, limited largely to cobalt catalysis [31][32]. While there are several reports of palladium-catalyzed systems for room-temperature direct arylation (i.e., no directing
- group, transition-metal catalyzed), a radical mechanism has not been previously discussed. Some of these reports indicate a marked difference in selectivity between elevated and ambient temperatures, which we found may be due to a change in mechanism (Supporting Information File 1, Table S1, Figure S1
Graphical Abstract
Scheme 1: A high yielding, highly selective room-temperature direct arylation reaction between indole and iod...
Figure 1: 1H NMR (500 MHz, CDCl3) of (a) 5-iodo-1-octylindole monomer (b) PIn prepared according to condition...
Figure 2: MALDI–TOF MS of PIn, indicating octylindole repeat units with three different types of end groups. ...
Scheme 2: Commonly discussed mechanisms for C2 selective direct arylation, none containing radical intermedia...
Scheme 3: Proposed mechanism for palladium radical involved reaction between indole and iodobenzene.
Scheme 4: Radical trap effects on literature methods for the direct arylation at room temperature. A) From re...
Palladium-catalyzed Sonogashira coupling reactions in γ-valerolactone-based ionic liquids
- László Orha,
- József M. Tukacs,
- László Kollár and
- László T. Mika
Beilstein J. Org. Chem. 2019, 15, 2907–2913, doi:10.3762/bjoc.15.284
- chemistry; ionic liquids; Introduction In the past few decades, the transition-metal-catalyzed coupling reaction has represented one of the most powerful and atom economical strategies for the efficient assembly of new carbon–carbon bonds. It has therefore become the most attractive approach to the
- reaction environment could have a significant effect on the efficiency of a transition-metal-catalyzed reaction. Because [TBP][4EtOV] was isolated from an aqueous solution, the investigation of possible influence of the residual water content on the reaction was highly desired. We found that no decrease in
Graphical Abstract
Scheme 1: Palladium-catalyzed Sonogashira cross-coupling of iodobenzene (1a) and phenylacetylene (2a) in ioni...
Figure 1: Effect of catalyst precursors used in Sonogashira coupling reaction of iodobenzene (1a, 0.5 mmol) a...
Figure 2: Re-use of Pd catalyst for Sonogashira coupling of iodobenzene (1a) and phenylacetylene (2a). Reacti...
Emission solvatochromic, solid-state and aggregation-induced emissive α-pyrones and emission-tuneable 1H-pyridines by Michael addition–cyclocondensation sequences
- Natascha Breuer,
- Irina Gruber,
- Christoph Janiak and
- Thomas J. J. Müller
Beilstein J. Org. Chem. 2019, 15, 2684–2703, doi:10.3762/bjoc.15.262
- fluorophores [19], in particular on aggregation-induced emissive polar dyes [20]. Conceptually, many of these consecutive multicomponent syntheses rely on transition-metal-catalyzed heterocyclic syntheses [21]. By virtue of catalytic generation of alkynones [22] we have recently disclosed consecutive
Graphical Abstract
Scheme 1: Consecutive three-component alkynylation–Michael addition–cyclocondensation (AMAC) synthesis of α-p...
Scheme 2: Consecutive pseudo-four-component alkynylation–Michael addition–cyclocondensation (AMAC) synthesis ...
Scheme 3: Consecutive pseudo-four-component alkynylation–Michael addition–cyclocondensation (AMAC) synthesis ...
Scheme 4: Model system for the optimization of the Michael addition–cyclocondensation reaction step to 1H-pyr...
Scheme 5: Formation of α-pyrone 6a and 1H-pyridine 5a at 20 °C.
Scheme 6: Formation of α-pyrone 6a starting from alkynone 3b having an electron-donating substituent.
Scheme 7: Formation of 1H-pyridine 5b starting from alkynone 3d having an electron-withdrawing substituent.
Scheme 8: Formation of 1H-pyridine 8a by Michael addition–cyclocondensation reaction.
Scheme 9: Mechanistic rationale for the formation of the 1H-pyridine 5a.
Scheme 10: Formation of 1H-pyridine 8a from alkynone 3b and dimer 7.
Figure 1: Molecular structure of 1H-pyridine 5a (50% thermal ellipsoids), showing the intramolecular N–H···O ...
Figure 2: Supramolecular C–H···N [36-39] and C–H···π [40-49] interactions around the 6-positioned phenyl ring in 5a. Detail...
Figure 3: 1H-Pyridine derivatives 5 as solids under daylight (top), under UV light (λexc = 365 nm, c(5) = 10−4...
Figure 4: Selected normalized absorption (solid lines) and emission (dashed lines) spectra of 1H-pyridines 5a...
Figure 5: Selected normalized emission spectra of 1H-pyridine 5a and 5b in the solid state at T = 298 K.
Figure 6: Selected normalized absorption (solid lines) and emission (dashed lines) spectra of 1H-pyridines 8a...
Figure 7: Solid-state luminescence of 1H-pyridines 5a, 8a and 8b (λexc = 365 nm).
Figure 8: α-Pyrones 6 as solids under daylight (top), selected derivatives under UV light (λexc = 365 nm, c(6...
Figure 9: Selected normalized absorption spectra of α-pyrones 6a, 6b, 6d, and 6e recorded in dichloromethane ...
Figure 10: Selected normalized absorption (solid lines) and emission (dashed lines) spectra of α-pyrones 6c, 6e...
Figure 11: Absorption (top) and fluorescence (bottom) of compound 6c with variable solvent polarity (left to t...
Figure 12: Absorption (solid lines) and emission (dashed lines) spectra of α-pyrone 6c in five solvents of dif...
Figure 13: Lippert plot for α-pyrone 6c (n = x, r2 = 0.970).
Figure 14: Normalized emission spectra of selected α-pyrones 6a–d,f in the solid state at T = 298 K.
Figure 15: Fluorescence of compound 6e in different THF/water fractions (top, λexc = 365 nm, handheld UV lamp)...
Figure 16: Selected DFT-computed (B3LYP 6-311G**) Kohn–Sham FMOs for 1H-pyridines 5f and 5g representing contr...
Figure 17: Selected DFT-computed (B3LYP 6-311G**) Kohn–Sham FMOs for 1H-pyridines 6a, 6c, 6e, 6f, and 6g and r...
Chiral terpene auxiliaries V: Synthesis of new chiral γ-hydroxyphosphine oxides derived from α-pinene
- Anna Kmieciak and
- Marek P. Krzemiński
Beilstein J. Org. Chem. 2019, 15, 2493–2499, doi:10.3762/bjoc.15.242
- with chlorophosphines, the reaction of metal phosphides with haloalkanes, and transition-metal-catalyzed cross-coupling reactions to form C–P bonds are the most widely used methods for the synthesis of phosphines [13][14]. Since phosphines are easily oxidized to phosphine oxides, the addition of
Graphical Abstract
Scheme 1: Synthesis of (1R,2R,4S,5R)-3-methyleneneoisoverbanol (6).
Scheme 2: Synthesis of (1R,2R,3R,5R)-4-methyleneneoisopinocampheol (11).
Scheme 3: Synthesis of allylic alcohols 16 and 18 from β-pinene.
Figure 1: NOE effects in molecules 16 and 18.
Scheme 4: Synthesis of (1R,2R,3R,4R,5R)-3-((diphenylphosphanyl)methyl)isoverbanol (23).
Scheme 5: Synthesis of (((1R,2R,3S,4S,5S)-3-hydroxypinan-4-yl)methyl)diphenylphosphine oxide (27).
Scheme 6: Attempted sigmatropic rearrangement of phosphinites 28 and 29.
Synthesis of acremines A, B and F and studies on the bisacremines
- Nils Winter and
- Dirk Trauner
Beilstein J. Org. Chem. 2019, 15, 2271–2276, doi:10.3762/bjoc.15.219
- ]. Nevertheless, to the best of our knowledge, no asymmetric entry to this class of natural products has been described. Our retrosynthetic analysis of 5 is depicted in Scheme 1. The prenyl side chain would be introduced by transition metal-catalyzed cross coupling of vinyl iodide 9. Compound 9 in turn could be
Graphical Abstract
Figure 1: Selected members of the acremine family [3-5].
Scheme 1: Retrosynthetic analysis of acremine F (5).
Scheme 2: Total synthesis of acremine F (5).
Scheme 3: Synthesis of acremines A and B through selective oxidation of acremine F.
Scheme 4: Proposed biomimetic dimerization of 5.
Scheme 5: Attempted intramolecular cyclization of 23.
Scheme 6: Attempted photochemical cyclization of 25.
Recent advances in transition-metal-catalyzed incorporation of fluorine-containing groups
- Xiaowei Li,
- Xiaolin Shi,
- Xiangqian Li and
- Dayong Shi
Beilstein J. Org. Chem. 2019, 15, 2213–2270, doi:10.3762/bjoc.15.218
- , agricultural, and materials industries. The incorporation of fluorine-containing groups into organic molecules can improve their chemical and physical properties, which attracts continuous interest in organic synthesis. Among various reported methods, transition-metal-catalyzed fluorination/fluoroalkylation
- has emerged as a powerful method for the construction of these compounds. This review attempts to describe the major advances in the transition-metal-catalyzed incorporation of fluorine, trifluoromethyl, difluoromethyl, trifluoromethylthio, and trifluoromethoxy groups reported between 2011 and 2019
- brief summary of the recent achievements in the ever-growing field of green fluoroalkylation. However, until now, no comprehensive survey of the literature has been reported on this topic. In this review, we highlight the recent progress of transition-metal-catalyzed fluorination and
Graphical Abstract
Scheme 1: The main three strategies of fluorination: nucleophilic, electrophilic and radical fluorination.
Scheme 2: Doyle’s Pd-catalyzed fluorination of allylic chlorides.
Scheme 3: Allylic fluorination of 2- and 3-substituted propenyl esters.
Scheme 4: Regioselective allylic fluorination of cinnamyl phosphorothioate esters.
Scheme 5: Palladium-catalyzed aliphatic C–H fluorination reported by Doyle.
Scheme 6: Pd-catalyzed enantioselective fluorination of α-ketoesters followed by stereoselective reduction to...
Scheme 7: Pd-catalyzed C(sp3)–H fluorination of oxindoles.
Scheme 8: C–H fluorination of 8-methylquinoline derivatives with F− reagents.
Scheme 9: Fluorination of α-cyano acetates reported by van Leeuwen.
Scheme 10: The catalytic enantioselective electrophilic C–H fluorination of α-chloro-β-keto phosphonates.
Scheme 11: Fluorination of unactivated C(sp3)–H bonds directed by the bidentate PIP auxiliary.
Scheme 12: Fluorination of C(sp3)–H bonds at the β-position of carboxylic acids.
Scheme 13: Enantioselective benzylic C–H fluorination with a chiral transient directing group.
Scheme 14: Microwave-heated Pd-catalyzed fluorination of aryl alcohols.
Scheme 15: Fluorination of aryl potassium trifluoroborates.
Scheme 16: C(sp2)–F bond formation using precatalyst [L·Pd]2(cod).
Scheme 17: Pd-catalyzed fluorination of (hetero)aryl triflates and bromides.
Scheme 18: The Pd-catalyzed C–H fluorination of arenes with Selectfluor/NFSI.
Scheme 19: Pd(II)-catalyzed ortho-monofluorination protocol for benzoic acids.
Scheme 20: Pd-catalyzed C(sp2)–H bond fluorination of 2-arylbenzothiazoles.
Scheme 21: Nitrate-promoted fluorination of aromatic and olefinic C(sp2)–H bonds and proposed mechanism.
Scheme 22: Fluorination of oxalyl amide-protected benzylamine derivatives.
Scheme 23: C–H fluorination of benzaldehydes with orthanilic acids as transient directing group.
Scheme 24: Pd(II)-catalyzed aryl C–H fluorination with various directing groups.
Scheme 25: Cu-catalyzed aliphatic, allylic, and benzylic fluorination.
Scheme 26: Cu-catalyzed SN2 fluorination of primary and secondary alkyl bromides.
Scheme 27: Copper-catalyzed fluorination of alkyl triflates.
Scheme 28: Cu-catalyzed fluorination of allylic bromides and chlorides.
Scheme 29: Synthetic strategy for the fluorination of active methylene compounds.
Scheme 30: Fluorination of β-ketoesters using a tartrate-derived bidentate bisoxazoline-Cu(II) complex.
Scheme 31: Highly enantioselective fluorination of β-ketoesters and N-Boc-oxindoles.
Scheme 32: Amide group-assisted site-selective fluorination of α-bromocarbonyl compounds.
Scheme 33: Cu-mediated aryl fluorination reported by Sanford [77].
Scheme 34: Mono- or difluorination reactions of benzoic acid derivatives.
Scheme 35: Cu-catalyzed fluorination of diaryliodonium salts with KF.
Scheme 36: Copper(I)-catalyzed cross-coupling of 2-pyridylaryl bromides.
Scheme 37: AgNO3-catalyzed decarboxylative fluorination of aliphatic carboxylic acids.
Scheme 38: The Mn-catalyzed aliphatic and benzylic C–H fluorination.
Scheme 39: Iron(II)-promoted C–H fluorination of benzylic substrates.
Scheme 40: Ag-catalyzed fluorodecarboxylation of carboxylic acids.
Scheme 41: Vanadium-catalyzed C(sp3)–H fluorination.
Scheme 42: AgNO3-catalyzed radical deboronofluorination of alkylboronates and boronic acids.
Scheme 43: Selective heterobenzylic C–H fluorination with Selectfluor reported by Van Humbeck.
Scheme 44: Fe(II)-catalyzed site-selective fluorination guided by an alkoxyl radical.
Scheme 45: Fluorination of allylic trichloroacetimidates reported by Nguyen et al.
Scheme 46: Iridium-catalyzed fluorination of allylic carbonates with TBAF(t-BuOH)4.
Scheme 47: Iridium-catalyzed asymmetric fluorination of allylic trichloroacetimidates.
Scheme 48: Cobalt-catalyzed α-fluorination of β-ketoesters.
Scheme 49: Nickel-catalyzed α-fluorination of various α-chloro-β-ketoesters.
Scheme 50: Ni(II)-catalyzed enantioselective fluorination of oxindoles and β-ketoesters.
Scheme 51: Scandium(III)-catalyzed asymmetric C–H fluorination of unprotected 3-substituted oxindoles.
Scheme 52: Iron-catalyzed directed C–H fluorination.
Scheme 53: Electrophilic silver-catalyzed Ar–F bond-forming reaction from arylstannanes.
Figure 1: Nucleophilic, electrophilic and radical CF3 sources.
Scheme 54: Cu(I)-catalyzed allylic trifluoromethylation of unactivated terminal olefins.
Scheme 55: Direct copper-catalyzed trifluoromethylation of allylsilanes.
Scheme 56: Cupper-catalyzed enantioselective trifluoromethylation of five and six-membered ring β-ketoesters.
Scheme 57: Cu-catalyzed highly stereoselective trifluoromethylation of secondary propargyl sulfonates.
Scheme 58: Remote C(sp3)–H trifluoromethylation of carboxamides and sulfonamides.
Scheme 59: Trifluoromethylation of allylsilanes with photoredox catalysis.
Scheme 60: Ag-catalyzed decarboxylative trifluoromethylation of aliphatic carboxylic acids in aqueous CH3CN.
Scheme 61: Decarboxylative trifluoromethylation of aliphatic carboxylic acids via combined photoredox and copp...
Scheme 62: Palladium-catalyzed Ar–CF3 bond-forming reaction.
Scheme 63: Palladium-catalyzed trifluoromethylation of arenes with diverse heterocyclic directing groups.
Scheme 64: Pd-catalyzed trifluoromethylation of indoles as reported by Liu.
Scheme 65: Pd-catalyzed trifluoromethylation of vinyl triflates and vinyl nonaflates.
Scheme 66: Pd(II)-catalyzed ortho-trifluoromethylation of aromatic C–H bonds.
Scheme 67: Visible-light-induced Pd(OAc)2-catalyzed ortho-trifluoromethylation of acetanilides with CF3SO2Na.
Scheme 68: CuI-catalyzed trifluoromethylation of aryl- and alkenylboronic acids.
Scheme 69: Cu-catalyzed trifluoromethylation of aryl- and vinylboronic acids.
Scheme 70: Copper-catalyzed trifluoromethylation of α,β-unsaturated carboxylic acids.
Scheme 71: Formation of C(sp2)–CF3 bond catalyzed by copper(I) complex.
Scheme 72: Loh’s Cu(I)-catalyzed trifluoromethylation of enamides and electron-deficient alkenes.
Scheme 73: Copper and iron-catalyzed decarboxylative tri- and difluoromethylation.
Scheme 74: Cu-catalyzed trifluoromethylation of hydrazones developed by Bouyssi.
Scheme 75: Cu(I)-catalyzed trifluoromethylation of terminal alkenes.
Scheme 76: Cu/Ag-catalyzed decarboxylative trifluoromethylation of cinnamic acids.
Scheme 77: Copper-catalyzed direct alkenyl C–H trifluoromethylation.
Scheme 78: Copper(I/II)-catalyzed direct trifluoromethylation of styrene derivatives.
Scheme 79: Regioselective trifluoromethylation of pivalamido arenes and heteroarenes.
Scheme 80: Synthesis of trifluoromethylquinones in the presence of copper(I).
Scheme 81: Oxidative trifluoromethylation of imidazoheterocycles in ionic liquid/water.
Scheme 82: A mild and fast continuous-flow trifluoromethylation of coumarins using a CuI/CF3SO2Na/TBHP system.
Scheme 83: Copper-catalyzed oxidative trifluoromethylation of various 8-aminoquinolines.
Scheme 84: PA-directed copper-catalyzed trifluoromethylation of anilines.
Scheme 85: Trifluoromethylation of potassium vinyltrifluoroborates catalyzed by Fe(II).
Scheme 86: Alkenyl trifluoromethylation catalyzed by Ru(phen)3Cl2 as photocatalyst.
Scheme 87: Ru-catalyzed trifluoromethylation of alkenes by Akita’s group.
Scheme 88: Ir-catalyzed Cvinyl–CF3 bond formation of α,β-unsaturated carboxylic acids.
Scheme 89: Ag(I)-catalyzed denitrative trifluoromethylation of β-nitrostyrenes.
Scheme 90: Photocatalyzed direct trifluoromethylation of aryl and heteroaryl C–H bonds.
Scheme 91: Rhenium (MTO)-catalyzed direct trifluoromethylation of aromatic substrates.
Scheme 92: Trifluoromethylation of unprotected anilines under [Ir(ppy)3] catalyst.
Scheme 93: Oxidative trifluoromethylation of imidazopyridines and imidazoheterocycles.
Scheme 94: Ruthenium-catalyzed trifluoromethylation of (hetero)arenes with trifluoroacetic anhydride.
Scheme 95: Phosphovanadomolybdic acid-catalyzed direct C–H trifluoromethylation.
Scheme 96: Picolinamide-assisted ortho-trifluoromethylation of arylamines.
Scheme 97: A nickel-catalyzed C–H trifluoromethylation of free anilines.
Scheme 98: Cu-mediated trifluoromethylation of terminal alkynes reported by Qing.
Scheme 99: Huang’s C(sp)–H trifluoromethylation using Togni’s reagent.
Scheme 100: Cu-catalyzed methods for trifluoromethylation with Umemoto’s reagent.
Scheme 101: The synthesis of alkynyl-CF3 compounds in the presence of fac-[Ir(ppy)3] under visible-light irradi...
Scheme 102: Pd-catalyzed Heck reaction reported by Reutrakul.
Scheme 103: Difluoromethylation of enamides and ene-carbamates.
Scheme 104: Difluoromethylation of α,β-unsaturated carboxylic acids.
Scheme 105: Copper-catalyzed direct C(sp2)–H difluoroacetylation reported by Pannecoucke and co-workers.
Scheme 106: Difluoroalkylation of aldehyde-derived hydrazones with functionalized difluoromethyl bromides.
Scheme 107: Photoredox-catalyzed C–H difluoroalkylation of aldehyde-derived hydrazones.
Scheme 108: Synergistic ruthenium(II)-catalyzed C–H difluoromethylation reported by Ackermann.
Scheme 109: Visible-light photocatalytic decarboxylation of α,β-unsaturated carboxylic acids.
Scheme 110: Synthesis of difluorinated ketones via S-alkyl dithiocarbamates obtained from acyl chlorides and po...
Scheme 111: Synthesis of aryl and heteroaryl difluoromethylated phosphonates.
Scheme 112: Difluoroalkylation of secondary propargyl sulfonates using Cu as the catalyst.
Scheme 113: Ru(II)-mediated para-selective difluoromethylation of anilides and their derivatives.
Scheme 114: Bulky diamine ligand promoted cross-coupling of difluoroalkyl bromides.
Scheme 115: Copper-catalyzed C3–H difluoroacetylation of quinoxalinones.
Scheme 116: Copper(I) chloride-catalyzed trifluoromethylthiolation of enamines, indoles and β-ketoesters.
Scheme 117: Copper-boxmi-catalyzed asymmetric trifluoromethylthiolation of β-ketoesters.
Scheme 118: Direct Cu-catalyzed trifluoromethylthiolation of boronic acids and alkynes.
Scheme 119: Cu-catalyzed synthesis of α-trifluoromethylthio-substituted ketones.
Scheme 120: Trifluoromethylthiolation reactions promoted by diazotriflone and copper.
Scheme 121: Halide activation of N-(trifluoromethylthio)phthalimide.
Scheme 122: The visible light-promoted trifluoromethylthiolation reported by Glorius.
Scheme 123: Synthesis of α-trifluoromethylthioesters via Goossen’s approach.
Scheme 124: Photoinduced trifluoromethylthiolation of diazonium salts.
Scheme 125: Ag-mediated trifluoromethoxylation of aryl stannanes and arylboronic acids.
Scheme 126: Catalytic (hetero)aryl C–H trifluoromethoxylation under visible light.
Scheme 127: Photoinduced C–H-bond trifluromethoxylation of (hetero)arenes.
Cyclopropanation–ring expansion of 3-chloroindoles with α-halodiazoacetates: novel synthesis of 4-quinolone-3-carboxylic acid and norfloxacin
- Sara Peeters,
- Linn Neerbye Berntsen,
- Pål Rongved and
- Tore Bonge-Hansen
Beilstein J. Org. Chem. 2019, 15, 2156–2160, doi:10.3762/bjoc.15.212
- decomposition of diazo compounds, are particularly versatile intermediates in organic synthesis, as they partake in cyclopropanation and C–H insertion reactions with high levels of selectivity [2]. This transition-metal-catalyzed carbene transfer has emerged as a mild and attractive route to indole
Graphical Abstract
Scheme 1: The effect of indole substituents on the yields of ethyl quinoline-3-carboxylates [15]. Green = good, o...
Figure 1: Quinolone 3-carboxylate scaffold, norfloxacin (1) and ciprofloxacin (2).
Scheme 2: Retrosynthetic outline for the synthesis of quinolone-3-carboxlates from indole derivatives.
Scheme 3: Synthesis of ethyl 4-quinolone-3-carboxylate (6) and proposed mechanism. a: Rh2(esp)2 (1 mol %), CH2...
Scheme 4: Synthesis of norfloxacin. a: Cl-EDA (1.3 equiv), Rh2(esp)2 (1 mol %), toluene, rt, Cs2CO3, 75%. b: ...
Synthesis of benzo[d]imidazo[2,1-b]benzoselenoazoles: Cs2CO3-mediated cyclization of 1-(2-bromoaryl)benzimidazoles with selenium
- Mio Matsumura,
- Yuki Kitamura,
- Arisa Yamauchi,
- Yoshitaka Kanazawa,
- Yuki Murata,
- Tadashi Hyodo,
- Kentaro Yamaguchi and
- Shuji Yasuike
Beilstein J. Org. Chem. 2019, 15, 2029–2035, doi:10.3762/bjoc.15.199
- , reaction 3) [8]. However, to the best of our knowledge, the synthesis of imidazoselenoazoles has been limited to highly substituted derivatives and the basic physical properties of the parent skeleton have not been clarified. Transition metal-catalyzed reactions are one of the most popular methods to form
Graphical Abstract
Scheme 1: Previously reported synthetic methods for the preparation of imidazo[2,1-b]selenoazoles.
Figure 1: (a) Ortep drawing of 2a (50% probability, only one of two independent molecules is shown) and (b) p...
Figure 2: Cs2CO3-mediated cyclization of 1-(2-bromoaryl)imidazoles with Se. Reaction conditions: 1 (0.5 mmol)...
Figure 3: Absorption spectra of selected compounds (2a, 10 and 11) in CHCl3.
Scheme 2: Control reactions.
Scheme 3: Proposed mechanism.
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
- 45. Thanks to the great advance of transition metal-mediated or catalyzed reactions that have been widely used for the construction of C–C, C–N, C–O, C–S, and C–X (X = F, Cl, Br or I) bonds in synthetic organic chemistry, and especially the transition metal-catalyzed functionalization of unreactive C
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
- Gagandeep Kour Reen Ashok Kumar Pratibha Sharma School of Chemical Sciences, Devi Ahilya University, Indore, (M. P.), India 10.3762/bjoc.15.165 Abstract A comprehensive account of recent advances in the synthesis of imidazopyridines, assisted through transition-metal-catalyzed multicomponent
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.
Borylation and rearrangement of alkynyloxiranes: a stereospecific route to substituted α-enynes
- Ruben Pomar Fuentespina,
- José Angel Garcia de la Cruz,
- Gabriel Durin,
- Victor Mamane,
- Jean-Marc Weibel and
- Patrick Pale
Beilstein J. Org. Chem. 2019, 15, 1416–1424, doi:10.3762/bjoc.15.141
- -Enynes are also important building blocks in organic syntheses or platforms for further synthesis [19]. Accordingly, significant efforts have been made to develop efficient syntheses of enynes [17][18][19][20]. The most common routes relied on Wittig-type reactions [21][22] and transition-metal-catalyzed
Graphical Abstract
Scheme 1: Stereospecific formation of α-enynes from alkynyloxiranes.
Scheme 2: Trapping experiments of the oxiranyllithium derived from cis or trans-alkynyloxiranes 1b, and their...
Scheme 3: Proposed mechanism for the rearrangement of alkynyloxiranes to α-enynes through metalation and bory...
