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Search for "alkene" in Full Text gives 524 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.
Synthetic approaches to bowl-shaped π-conjugated sumanene and its congeners
- Shakeel Alvi and
- Rashid Ali
Beilstein J. Org. Chem. 2020, 16, 2212–2259, doi:10.3762/bjoc.16.186
- catalyst 15 to yield the trimerized products 12 (syn) and 13 (anti) in respectable yields (Scheme 2). The alkene-bridge exchange of 12 (syn) was accomplished by tandem ring-opening and ring-closing metathesis (ROM–RCM) in the presence of Grubbs’ first generation (G-I) catalyst to generate a C3-symmetric
- 27 in a single step. They also pointed out that when ethylene gas was used as an alkene source for the ring-opening step, diluted reaction conditions were necessary to dissolve the ethylene in dichloromethane to avoid polymerization. Therefore, after several experimentations, they noticed that liquid
- Z-oct-4-ene in toluene was found to be a more effective alkene source for the ring-opening reaction in comparison to the gaseous ethylene, as it increases solubility and also improve the lifetime of the catalyst. 2.1 Derivatization at benzylic position As can be inferred from the architecture of
Graphical Abstract
Figure 1: Representation of corannulene (1) and sumanene (2), the subunits of fullerene (C60).
Scheme 1: Mehta’s unsuccessful effort for the synthesis of sumanene scaffold 2.
Scheme 2: First synthesis of sumanene 2 by Sakurai et al. from norbornadiene 10.
Scheme 3: Synthesis of trimethylsumanene 28 from easily accessible norbornadiene (10).
Scheme 4: Generation of anions 29–31 and the preparation of tris(trimethylsilyl)sumanene 32.
Scheme 5: Synthesis of tri- and hexa-substituted sumanene derivatives.
Scheme 6: Synthesis of bowl-shaped π-extended sumanene derivatives 37a–f.
Scheme 7: Synthesis of monooxasumanene 38, trioxosumanene 40 along with imination of them.
Scheme 8: Synthesis of trimethylsumanenetrione 46 and exo-functionalized products 45a,b.
Scheme 9: Synthesis of bisumanenylidene 47 and sumanene dimer 48 from 2.
Scheme 10: The mono-substitution of 2 to generate diverse mono-sumanene derivatives 49a–d.
Scheme 11: Synthesis of sumanene building block 53 useful for further extension.
Scheme 12: Synthesis of hexafluorosumanene derivative 55 by Sakurai and co-workers.
Scheme 13: Preparation of sumanene-based carbene 60 and its reaction with cyclohexane.
Scheme 14: Barton–Kellogg reaction for the synthesis of sterically hindered alkenes.
Scheme 15: Synthesis of hydroxysumanene 68 by employing Baeyer–Villiger oxidation.
Scheme 16: Synthesis of sumanene derivatives having functionality at an internal carbon.
Scheme 17: Mechanism for nucleophilic substitution reaction at the internal carbon.
Scheme 18: Synthesis of diverse monosubstituted sumanene derivatives.
Scheme 19: Synthesis of di- and trisubstituted sumanene derivatives from sumanene (2).
Scheme 20: Preparation of monochlorosumanene 88 and hydrogenation of sumanene (2).
Scheme 21: The dimer 90 and bissumanenyl 92 achieved from halosumannes.
Scheme 22: Pyrenylsumanene 93 involving the Suzuki-coupling as a key transformation.
Scheme 23: Synthesis of various hexaarylsumanene derivatives using the Suzuki-coupling reaction.
Scheme 24: Synthesis of hexasubstituted sumanene derivatives 96 and 97.
Scheme 25: Synthesis of thioalkylsumanenes via an aromatic nucleophilic substitution reaction.
Scheme 26: Synthesis of tris(ethoxycarbonylethenyl)sumanene derivative 108.
Scheme 27: Synthesis of ferrocenyl-based sumanene derivatives.
Scheme 28: Synthesis of sumanenylferrocene architectures 118 and 119 via Negishi coupling.
Scheme 29: Diosmylation and the synthesis of phenylboronate ester 121 of sumanene.
Scheme 30: Synthesis of the iron-complex of sumanene.
Scheme 31: Synthesis of tri- and mononuclear sumanenyl zirconocene complexes.
Scheme 32: Synthesis of [CpRu(η6-sumanene)]PF6.
Scheme 33: Preparation of sumanene-based porous coordination networks 127 (spherical tetramer units) and 128 (...
Scheme 34: Synthesis of sumanenylhafnocene complexes 129 and 130.
Scheme 35: Synthesis of 134 and 135 along with PdII coordination complex 136.
Scheme 36: Synthesis of alkali metals sumanene complex K7(C21H102−)2(C21H93−)·8THF (137) containing di- and tr...
Scheme 37: The encapsulation of a Cs+ ion between two sumanenyl anions.
Scheme 38: Synthesis of monothiasumanene 140 and dithiasumanene 141 from 139.
Scheme 39: Synthesis of trithiasumanene 151 by Otsubo and his co-workers.
Scheme 40: Synthesis of trithiasumanene derivatives 155 and 156.
Scheme 41: Synthetic route towards hexathiolated trithiasumanenes 158.
Scheme 42: Synthesis of triselenasumanene 160 by Shao and teammates.
Scheme 43: Synthesis of tritellurasumanene derivatives from triphenylene skeletons.
Scheme 44: Synthesis of pyrazine-fused sumanene architectures through condensation reaction.
Scheme 45: Treatment of the trichalcogenasumanenes with diverse oxidative reagents.
Scheme 46: Ring-opening reaction with H2O2 and oxone of heterasumanenes 178 and 179.
Scheme 47: Synthesis of polycyclic compounds from sumanene derivatives.
Scheme 48: Synthesis of diimide-based heterocycles reported by Shao’s and co-workers.
Scheme 49: Synthesis of pristine trichalcogenasumanenes, 151, 205, and 206.
Scheme 50: Synthesis of trichalcogenasumanenes via hexaiodotriphenylene precursor 208.
Scheme 51: Synthesis of trisilasumanenes 214 and 215.
Scheme 52: Synthesis of trisilasumanene derivatives 218 and 219.
Scheme 53: Synthesis of novel trigermasumanene derivative 223.
Scheme 54: An attempt towards the synthesis of tristannasumanene derivative 228.
Scheme 55: Synthesis of triphosphasumanene trisulfide 232 from commercially available 229.
Scheme 56: The doping of sumanene derivatives with chalcogens (S, Se, Te) and phosphorus.
Scheme 57: Synthesis of heterasumanene containing three different heteroatoms.
Scheme 58: Synthesis of trichalcogenasumanene derivatives 240 and 179.
Scheme 59: Preparation of trichalcogenasumanenes 245 and 248.
Scheme 60: Design and synthesis of trichalcogenasumanene derivatives 252 and 178.
Scheme 61: Synthesis of spirosumanenes 264–269 and non-spiroheterasumanenes 258–263.
Scheme 62: Synthesis of sumanene-type hetero polycyclic compounds.
Scheme 63: Synthesis of triazasumanenes 288 and its sulfone congener 287.
Scheme 64: Synthesis of C3-symmetric chiral triaryltriazasumanenes via cross-coupling reaction.
Scheme 65: Synthesis of mononaphthosumanene 293 using Suzuki coupling as a key step.
Scheme 66: Synthesis of di- and trinaphthosumanene derivatives 302–304.
Scheme 67: Synthesis of hemifullerene skeletons by Hirao’s group.
Scheme 68: Design and construction of C70 fragment from a C60 sumanene fragment.
Selective preparation of tetrasubstituted fluoroalkenes by fluorine-directed oxetane ring-opening reactions
- Clément Q. Fontenelle,
- Thibault Thierry,
- Romain Laporte,
- Emmanuel Pfund and
- Thierry Lequeux
Beilstein J. Org. Chem. 2020, 16, 1936–1946, doi:10.3762/bjoc.16.160
- -opening reaction with bromide ions, even in the presence of bulky substituents. Keywords: acyclonucleotide; fluorine; monofluoroalkene; oxetane; selective ring-opening reaction; tetrasubstituted alkene; Introduction The introduction of fluorine atoms into organic compounds is known to modify their
- mixture of products (Table 1, entry 7). In contrast, the ring-opening reaction was successful when performed in the presence of TBAB and BF3·Et2O and afforded the E-alkene product 3d with good selectivity (E/Z ratio > 96:4) and 76% yield (Table 1, entry 8). The geometric assignment of compound 3d was
- analysis (see Supporting Information File 1). The attack of the bromide ion this time occurred from the side of the alkene hydrogen atom (cis attack) and away from the bulky phthalimido group giving solely product E-4d. Likewise, the reaction of the alkyl-substituted substrate 5 proceeded with excellent E
Graphical Abstract
Figure 1: Representative fluorinated nucleos(t)ides and acyclonucleotides.
Figure 2: Acyclonucleotides as nucleotide surrogates.
Figure 3: Olefination approaches and ring-opening of oxetane derivatives.
Scheme 1: Preparation of fluoroakylidene-oxetanes and their ring-opening reactions.
Scheme 2: Synthesis of benzyloxy-substituted fluoroethylidene-oxetane derivative 8.
Scheme 3: Effect of the medium on the selective formation of derivative 10.
Scheme 4: Mechanism for the formation of dihydrofuran 10.
Scheme 5: Mechanism for the formation of unsaturated lactones 14 and 15.
Scheme 6: Opening reaction of ethyl 2-(oxetanyl-3-idene)acetate (16).
Scheme 7: Functionalization of bromomethyllactone 15 and its analogues.
Scheme 8: Functionalization by substitution reaction of the bromide E-1d vs ring-opening reaction of the oxet...
Scheme 9: Preparation of tetrasubstituted fluoroalkenes.
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
- metal catalyst X2M into an aromatic C–H bond of a substrate (generally facilitated by the presence of a directing group (DG)), delivers a metal–aryl complex. Coordination and subsequent insertion of an alkene into the M–aryl bond then provides the desired coupling product after β-hydride elimination
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
- the PKR of enynes containing a fluoride moiety. Keywords: alkene; alkyne; enyne; fluorine; Pauson–Khand; Introduction The prevalence of fluorine-containing molecules in drug-discovery programs is nowadays unquestionable [1][2][3]. The presence of fluorine atoms or fluorine-containing units at
- the intramolecular version, the fluorine atom or fluorinated group can also form a part of the linker. The reaction yields are dependent on the degree of substitution, bulkiness, and electronic effects of the substituents of both the alkyne and alkene moieties. In general, electron-deficient alkynes
- fluorinated group is positioned in the final compound depends on whether it is attached to the alkene or alkyne counterpart of the substrate (Scheme 5). Regarding the intramolecular PKR of fluorinated enynes, only a few examples have been described. The first example was reported in 2001 by Ishizaki and co
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].
Heterogeneous photocatalysis in flow chemical reactors
- Christopher G. Thomson,
- Ai-Lan Lee and
- Filipe Vilela
Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125
Graphical Abstract
Figure 1: A) Bar chart of the publications per year for the topics “Photocatalysis” (49,662 instances) and “P...
Figure 2: A) Professor Giacomo Ciamician and Dr. Paolo Silber on their roof laboratory at the University of B...
Scheme 1: PRC trifluoromethylation of N-methylpyrrole (1) using hazardous gaseous CF3I safely in a flow react...
Figure 3: A) Unit cells of the three most common crystal structures of TiO2: rutile, brookite, and anatase. R...
Figure 4: Illustration of the key semiconductor photocatalysis events: 1) A photon with a frequency exceeding...
Figure 5: Photocatalytic splitting of water by oxygen vacancies on a TiO2(110) surface. Reprinted with permis...
Figure 6: Proposed adsorption modes of A) benzene, B) chlorobenzene, C) toluene, D) phenol, E) anisole, and F...
Figure 7: Structures of the sulfonate-containing organic dyes RB5 (3) and MX-5B (4) and the adsorption isothe...
Figure 8: Idealised triclinic unit cell of a g-C3N4 type polymer, displaying possible hopping transport scena...
Figure 9: Idealised structure of a perfect g-C3N4 sheet. The central unit highlighted in red represents one t...
Figure 10: Timeline of the key processes of charge transport following the photoexcitation of g-C3N4, leading ...
Scheme 2: Photocatalytic bifunctionalisation of heteroarenes using mpg-C3N4, with the selected examples 5 and ...
Figure 11: A) Structure of four linear conjugated polymer photocatalysts for hydrogen evolution, displaying th...
Figure 12: Graphical representation of the common methods used to immobilise molecular photocatalysts (PC) ont...
Figure 13: Wireless light emitter-supported TiO2 (TiO2@WLE) HPCat spheres powered by resonant inductive coupli...
Figure 14: Graphical representation of zinc–perylene diimide (Zn-PDI) supramolecular assembly photocatalysis v...
Scheme 3: Upconversion of NIR photons to the UV frequency by NaYF4:Yb,Tm nanocrystals sequentially coated wit...
Figure 15: Types of reactors employed in heterogeneous photocatalysis in flow. A) Fixed bed reactors and the s...
Figure 16: Electrochemical potential of common semiconductor, transition metal, and organic dye-based photocat...
Scheme 4: Possible mechanisms of an immobilised molecular photoredox catalyst by oxidative or reductive quenc...
Scheme 5: Scheme of the CMB-C3N4 photocatalytic decarboxylative fluorination of aryloxyacetic acids, with the...
Scheme 6: Scheme of the g-C3N4 photocatalytic desilylative coupling reaction in flow and proposed mechanism [208].
Scheme 7: Proposed mechanism of the radical cyclisation of unsaturated alkyl 2-bromo-1,3-dicarbonyl compounds...
Scheme 8: N-alkylation of benzylamine and schematic of the TiO2-coated microfluidic device [213].
Scheme 9: Proposed mechanism of the Pt@TiO2 photocatalytic deaminitive cyclisation of ʟ-lysine (23) to ʟ-pipe...
Scheme 10: A) Proposed mechanism for the photocatalytic oxidation of phenylboronic acid (24). B) Photos and SE...
Scheme 11: Proposed mechanism for the DA-CMP3 photocatalytic aza-Henry reaction performed in a continuous flow...
Scheme 12: Proposed mechanism for the formation of the cyclic product 32 by TiO2-NC HPCats in a slurry flow re...
Scheme 13: Reaction scheme for the photocatalytic synthesis of homo and hetero disulfides in flow and scope of...
Scheme 14: Reaction scheme for the MoOx/TiO2 HPCat oxidation of cyclohexane (34) to benzene. The graph shows t...
Scheme 15: Proposed mechanism of the TiO2 HPC heteroarene C–H functionalisation via aryl radicals generated fr...
Scheme 16: Scheme of the oxidative coupling of benzylamines with the HOTT-HATN HPCat and selected examples of ...
Scheme 17: Photocatalysis oxidation of benzyl alcohol (40) to benzaldehyde (41) in a microflow reactor coated ...
Figure 17: Mechanisms of Dexter and Forster energy transfer.
Scheme 18: Continuous flow process for the isomerisation of alkenes with an ionic liquid-immobilised photocata...
Scheme 19: Singlet oxygen synthetic step in the total synthesis of canataxpropellane [265].
Scheme 20: Scheme and proposed mechanism of the singlet oxygen photosensitisation by CMP_X HPCats, with the st...
Scheme 21: Structures of CMP HPCat materials applied by Vilela and co-workers for the singlet oxygen photosens...
Scheme 22: Polyvinylchloride resin-supported TDCPP photosensitisers applied for singlet oxygen photosensitisat...
Scheme 23: Structure of the ionically immobilised TPP photosensitiser on amberlyst-15 ion exchange resins (TPP...
Scheme 24: Photosensitised singlet oxygen oxidation of citronellol (46) in scCO2, with automatic phase separat...
Scheme 25: Schematic of PS-Est-BDP-Cl2 being applied for singlet oxygen photosensitisation in flow. A) Pseudo-...
Scheme 26: Reaction scheme of the singlet oxygen oxidation of furoic acid (54) using a 3D-printed microfluidic...
Figure 18: A) Photocatalytic bactericidal mechanism by ROS oxidative cleavage of membrane lipids (R = H, amino...
Figure 19: A) Suggested mechanisms for the aqueous pollutant degradation by TiO2 in a slurry flow reactor [284-287]. B)...
Figure 20: Schematic of the flow system used for the degradation of aqueous oxytetracycline (56) solutions [215]. M...
Scheme 27: Degradation of a salicylic acid (57) solution by a coupled solar photoelectro-Fenton (SPEF) process...
Figure 21: A) Schematic flow diagram using the TiO2-coated NETmix microfluidic device for an efficient mass tr...
An overview on disulfide-catalyzed and -cocatalyzed photoreactions
- Yeersen Patehebieke
Beilstein J. Org. Chem. 2020, 16, 1418–1435, doi:10.3762/bjoc.16.118
- [3 + 2] methylenecyclopentane annulations of olefins with methylenecyclopropanes. This regioselective, mild, and protecting group-free annulation requires only an equimolar amount of the reacting alkene and does not require an excess of the reacting alkene, unlike other methods [9]. Furthermore, the
- intermediate 51 to the phenyl thiyl radical 43 yields the intermediate 49, thiophenol, the protonated pyridine 47, and bromide. Finally, HAT from the thiophenol to the intermediate 49 gives the difluoroalkylation product 50. Alkene functionalization reactions The olefin hydration is an important method to
- unsuccessful to be prepared by the Schlosser modification of the Wittig olefination (Scheme 26) [33]. A similar isomerization method was also used by Holmes in the synthesis of (−)-gloeosporone. Under irradiation conditions, diphenyl disulfide helped to convert the Z-alkene 76 to the E-alkene 77 (Scheme 27) [34
Graphical Abstract
Scheme 1: [3 + 2] cyclization catalyzed by diaryl disulfide.
Scheme 2: [3 + 2] cycloaddition catalyzed by disulfide.
Scheme 3: Disulfide-bridged peptide-catalyzed enantioselective cycloaddition.
Scheme 4: Disulfide-catalyzed [3 + 2] methylenecyclopentane annulations.
Scheme 5: Disulfide as a HAT cocatalyst in the [4 + 2] cycloaddition reaction.
Scheme 6: Proposed mechanism of the [4 + 2] cycloaddition reaction using disulfide as a HAT cocatalyst.
Scheme 7: Disulfide-catalyzed ring expansion of vinyl spiro epoxides.
Scheme 8: Disulfide-catalyzed aerobic oxidation of diarylacetylene.
Scheme 9: Disulfide-catalyzed aerobic photooxidative cleavage of olefins.
Scheme 10: Disulfide-catalyzed aerobic oxidation of 1,3-dicarbonyl compounds.
Scheme 11: Proposed mechanism of the disulfide-catalyzed aerobic oxidation of 1,3-dicarbonyl compounds.
Scheme 12: Disulfide-catalyzed oxidation of allyl alcohols.
Scheme 13: Disulfide-catalyzed diboration of alkynes.
Scheme 14: Dehalogenative radical cyclization catalyzed by disulfide.
Scheme 15: Hydrodifluoroacetamidation of alkenes catalyzed by disulfide.
Scheme 16: Plausible mechanism of the hydrodifluoroacetamidation of alkenes catalyzed by disulfide.
Scheme 17: Disulfide-cocatalyzed anti-Markovnikov olefin hydration reactions.
Scheme 18: Disulfide-catalyzed decarboxylation of carboxylic acids.
Scheme 19: Proposed mechanism of the disulfide-catalyzed decarboxylation of carboxylic acids.
Scheme 20: Disulfide-catalyzed decarboxylation of carboxylic acids.
Scheme 21: Disulfide-catalyzed conversion of maleate esters to fumarates and 5H-furanones.
Scheme 22: Disulfide-catalyzed isomerization of difluorotriethylsilylethylene.
Scheme 23: Disulfide-catalyzed isomerization of allyl alcohols to carbonyl compounds.
Scheme 24: Proposed mechanism for the disulfide-catalyzed isomerization of allyl alcohols to carbonyl compound...
Scheme 25: Diphenyl disulfide-catalyzed enantioselective synthesis of ophirin B.
Scheme 26: Disulfide-catalyzed isomerization in the total synthesis of (+)-hitachimycin.
Scheme 27: Disulfide-catalyzed isomerization in the synthesis of (−)-gloeosporone.
Synthesis of pyrrolidinedione-fused hexahydropyrrolo[2,1-a]isoquinolines via three-component [3 + 2] cycloaddition followed by one-pot N-allylation and intramolecular Heck reactions
- Xiaoming Ma,
- Suzhi Meng,
- Xiaofeng Zhang,
- Qiang Zhang,
- Shenghu Yan,
- Yue Zhang and
- Wei Zhang
Beilstein J. Org. Chem. 2020, 16, 1225–1233, doi:10.3762/bjoc.16.106
- oxidative addition of the Pd(0) species to alkene intermediate 8a leads to Pd-complex I. Intramolecular coordination of Pd-complex I with the C–C double bond forms complex II which is followed by the syn insertion of alkene to give complex III [50][51]. Subsequent β-hydride elimination of III gives complex
Graphical Abstract
Figure 1: Bioactive pyrrolo[2,1-a]isoquinolines and hexahydropyrrolo[2,1-a]isoquinolines.
Scheme 1: [3 + 2] Cycloaddition with amino esters or amino acids.
Scheme 2: Scaffolds derived from the initial [3 + 2] adducts.
Scheme 3: [3 + 2] Cycloaddition with amino esters or amino acids. Conditions: 1:3:4 (1.2:1:1.1), Et3N (1.5 eq...
Scheme 4: Synthesis of pyrrolo[2,1-a]isoquinolines 9. Reaction conditions: 5 (0.5 mmol, 1 equiv), 7 (3 equiv)...
Scheme 5: Synthesis of pyrrolo[2,1-a]isoquinolines 11. Reaction conditions: 6 (0.5 mmol, 1 equiv), 7 (3 equiv...
Scheme 6: Synthesis of pyrrolo[2,1-a]isoquinolines 12. Reaction conditions: 5 or 6 (0.5 mmol, 1 equiv), cinna...
Scheme 7: Plausible mechanism for the synthesis of 9a.
Photocatalysis with organic dyes: facile access to reactive intermediates for synthesis
- Stephanie G. E. Amos,
- Marion Garreau,
- Luca Buzzetti and
- Jerome Waser
Beilstein J. Org. Chem. 2020, 16, 1163–1187, doi:10.3762/bjoc.16.103
- cations and radical anions) Recently, the exploitation of alkenyl and aryl radical ions has emerged as a platform for the functionalization of small molecules. They appear as attractive intermediates for a direct alkene difunctionalization or arene C–H functionalization. In particular, radical cations are
- , exploiting the reactivity of alkene radical cations generated using organic dyes [96][97]. Their seminal work reported the oxidation of the alkenols 22.1 by the Fukuzumi dye (OD2, Scheme 22) [98]. The so-formed radical cation undergoes an intramolecular nucleophilic 5/6/7-exo-trig-cyclization to give the
- cyclic ethers 22.3. Mes-Acr-Me+ (OD2) is a strong enough oxidant (E(PC+*/PC) ≈ 2.1 V), allowing the oxidation of unactivated alkenes (1.2 ≤ Eox ≤ 1.9 V). In this transformation, the cocatalyst 22.2 acts as an H atom shuttle. This alkene radical cation-based strategy has been extended to various
Graphical Abstract
Figure 1: Selected examples of organic dyes. Mes-Acr+: 9-mesityl-10-methylacridinium, DCA: 9,10-dicyanoanthra...
Scheme 1: Activation modes in photocatalysis.
Scheme 2: Main strategies for the formation of C(sp3) radicals used in organophotocatalysis.
Scheme 3: Illustrative example for the photocatalytic oxidative generation of radicals from carboxylic acids:...
Scheme 4: Illustrative example for the photocatalytic reductive generation of C(sp3) radicals from redoxactiv...
Figure 2: Common substrates for the photocatalytic oxidative generation of C(sp3) radicals.
Scheme 5: Illustrative example for the photocatalytic oxidative generation of radicals from dihydropyridines ...
Scheme 6: Illustrative example for the photocatalytic oxidative generation of C(sp3) radicals from trifluorob...
Scheme 7: Illustrative example for the photocatalytic reductive generation of C(sp3) radicals from benzylic h...
Scheme 8: Illustrative example for the photocatalytic generation of C(sp3) radicals via direct HAT: the cross...
Scheme 9: Illustrative example for the photocatalytic generation of C(sp3) radicals via indirect HAT: the deu...
Scheme 10: Selected precursors for the generation of aryl radicals using organophotocatalysis.
Scheme 11: Illustrative example for the photocatalytic reductive generation of aryl radicals from aryl diazoni...
Scheme 12: Illustrative examples for the photocatalytic reductive generation of aryl radicals from haloarenes:...
Scheme 13: Illustrative example for the photocatalytic reductive generation of aryl radicals from aryl halides...
Scheme 14: Illustrative example for the photocatalytic reductive generation of aryl radicals from arylsulfonyl...
Scheme 15: Illustrative example for the reductive photocatalytic generation of aryl radicals from triaryl sulf...
Scheme 16: Main strategies towards acyl radicals used in organophotocatalysis.
Scheme 17: Illustrative example for the decarboxylative photocatalytic generation of acyl radicals from α-keto...
Scheme 18: Illustrative example for the oxidative photocatalytic generation of acyl radicals from acyl silanes...
Scheme 19: Illustrative example for the oxidative photocatalytic generation of carbamoyl radicals from 4-carba...
Scheme 20: Illustrative example of the photocatalytic HAT approach for the generation of acyl radicals from al...
Scheme 21: General reactivity of a) radical cations; b) radical anions; c) the main strategies towards aryl an...
Scheme 22: Illustrative example for the oxidative photocatalytic generation of alkene radical cations from alk...
Scheme 23: Illustrative example for the reductive photocatalytic generation of an alkene radical anion from al...
Figure 3: Structure of C–X radical anions and their neutral derivatives.
Scheme 24: Illustrative example for the photocatalytic reduction of imines and the generation of an α-amino C(...
Scheme 25: Illustrative example for the oxidative photocatalytic generation of aryl radical cations from arene...
Scheme 26: NCR classifications and generation.
Scheme 27: Illustrative example for the photocatalytic reductive generation of iminyl radicals from O-aryl oxi...
Scheme 28: Illustrative example for the photocatalytic oxidative generation of iminyl radicals from α-N-oxy ac...
Scheme 29: Illustrative example for the photocatalytic oxidative generation of iminyl radicals via an N–H bond...
Scheme 30: Illustrative example for the photocatalytic oxidative generation of amidyl radicals from Weinreb am...
Scheme 31: Illustrative example for the photocatalytic reductive generation of amidyl radicals from hydroxylam...
Scheme 32: Illustrative example for the photocatalytic reductive generation of amidyl radicals from N-aminopyr...
Scheme 33: Illustrative example for the photocatalytic oxidative generation of amidyl radicals from α-amido-ox...
Scheme 34: Illustrative example for the photocatalytic oxidative generation of aminium radicals: the N-aryltet...
Scheme 35: Illustrative example for the photocatalytic oxidative generation of nitrogen-centered radical catio...
Scheme 36: Illustrative example for the photocatalytic oxidative generation of nitrogen-centered radical catio...
Scheme 37: Illustrative example for the photocatalytic oxidative generation of hydrazonyl radical from hydrazo...
Scheme 38: Generation of O-radicals.
Scheme 39: Illustrative examples for the photocatalytic generation of O-radicals from N-alkoxypyridinium salts...
Scheme 40: Illustrative examples for the photocatalytic generation of O-radicals from alkyl hydroperoxides: th...
Scheme 41: Illustrative example for the oxidative photocatalytic generation of thiyl radicals from thiols: the...
Scheme 42: Main strategies and reagents for the generation of sulfonyl radicals used in organophotocatalysis.
Scheme 43: Illustrative example for the reductive photocatalytic generation of sulfonyl radicals from arylsulf...
Scheme 44: Illustrative example of a Cl atom abstraction strategy for the photocatalytic generation of sulfamo...
Scheme 45: Illustrative example for the oxidative photocatalytic generation of sulfonyl radicals from sulfinic...
Scheme 46: Illustrative example for the photocatalytic generation of electronically excited triplet states: th...
Scheme 47: Illustrative example for the photocatalytic generation of electronically excited triplet states: th...
Copper-catalysed alkylation of heterocyclic acceptors with organometallic reagents
- Yafei Guo and
- Syuzanna R. Harutyunyan
Beilstein J. Org. Chem. 2020, 16, 1006–1021, doi:10.3762/bjoc.16.90
- co-workers elaborated the copper-catalysed ring opening reaction of oxabicyclic alkene substrates using organolithium reagents, finding excellent anti selectivities and enantioselectivity (Scheme 12) [42]. During the optimisation studies, they discovered that when the Lewis acid BF3·OEt2 was employed
Graphical Abstract
Scheme 1: Copper-catalysed ACA of organometallics to piperidones. A) addition of organozinc reagents; B) addi...
Scheme 2: Copper-catalysed ACA of alkenylalanes to N-substituted-2,3-dehydro-4-piperidones.
Scheme 3: Copper-catalysed asymmetric addition of dialkylzinc reagents to N-acyl-4-methoxypyridinium salts fo...
Scheme 4: Copper-catalysed ACA of organozirconium reagents to N-substituted 2,3-dehydro-4-piperidones and lac...
Scheme 5: Copper-catalysed ACA of Grignard reagents to chromones and coumarins and further derivatisation of ...
Scheme 6: Copper-catalysed ACA of Grignard reagents to N-protected quinolones.
Scheme 7: Copper-catalysed ACAs of organometallics to conjugated unsaturated lactams.
Scheme 8: Copper-catalysed ACA of Et2Zn to 5,6-dihydro-2-pyranone.
Scheme 9: Copper-catalysed ACA of Grignard reagents to pyranone and 5,6-dihydro-2-pyranone.
Scheme 10: Copper-catalysed AAA of an organozirconium reagent to heterocyclic acceptors.
Scheme 11: Copper-catalysed ring opening of an oxygen-bridged substrate with trialkylaluminium reagents.
Scheme 12: Copper-catalysed ring opening of oxabicyclic substrates with organolithium reagents (selected examp...
Scheme 13: Copper-catalysed ring opening of polycyclic meso hydrazines.
Scheme 14: Copper-catalysed ACA of Grignard reagents to alkenyl-substituted aromatic N-heterocycles.
Scheme 15: Copper-catalysed ACA of Grignard reagents to β-substituted alkenylpyridines.
Scheme 16: Copper-catalysed ACA of organozinc reagents to alkylidene Meldrum’s acids.
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
- studies on this reaction are ongoing with initial suggestions of the coupling between the sulfonyl radical and the radical alkene as a key step for this transformation. In 2019, Ghaffari-Moghaddam, Oveisi and co-workers reported the synthesis of a new multifunctional MOF, namely Fe@PCN-222(Fe), and its
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.
Copper catalysis with redox-active ligands
- Agnideep Das,
- Yufeng Ren,
- Cheriehan Hessin and
- Marine Desage-El Murr
Beilstein J. Org. Chem. 2020, 16, 858–870, doi:10.3762/bjoc.16.77
- reminiscent of the entatic state model. The proposed mechanism (Scheme 12) involves the insertion of a nitrene or carbene group to the copper complex 22 to form intermediate 23. Subsequent alkene insertion yields species 25 and the group-transfer product (21a,h–j,n,o, 26a–g and 27a–o) is released upon ring
Graphical Abstract
Scheme 1: Copper complexes with amidophenolate type benzoxazole ligands for alcohol oxidations.
Scheme 2: Copper-catalyzed aerobic oxidation of alcohols and representative substrate scope.
Scheme 3: Introduction of H-bonding network in the ligand coordination sphere.
Scheme 4: Well-defined isatin copper complexes.
Scheme 5: Catalyst control in the biomimetic phenol ortho-oxidation.
Scheme 6: Structural diversity accessible by direct functionalization.
Scheme 7: Copper-catalyzed trifluoromethylation of heteroaromatics with redox-active iminosemiquinone ligands....
Scheme 8: Reversal of helical chirality upon redox stimuli and enantioselective Michael addition with a redox...
Scheme 9: Interaction of guanidine-copper catalyst with oxygen and representative coupling products. a4 mol %...
Scheme 10: Access to 1,2-oxy-aminoarenes by copper-catalyzed phenol–amine coupling.
Scheme 11: Copper-catalyzed aziridination through molecular spin catalysis with redox-active iminosemiquinone ...
Scheme 12: Nitrogen-group and carbon-group transfer in copper-catalyzed aziridination and cyclopropanation thr...
Aldehydes as powerful initiators for photochemical transformations
- Maria A. Theodoropoulou,
- Nikolaos F. Nikitas and
- Christoforos G. Kokotos
Beilstein J. Org. Chem. 2020, 16, 833–857, doi:10.3762/bjoc.16.76
- . Moreover, the excited 4-anisaldehyde (98) underwent energy transfer over the addition to the double bond of the alkene, as no Paterno–Büchi cycloadducts were observed. Furthermore, the detection of the photolysis products of the alkyl halides mentioned above indicated the presence of triplet state 4
Graphical Abstract
Scheme 1: Norrish type I and II dissociations.
Scheme 2: Proposed radical pair formation after the photolysis of benzaldehyde (8).
Scheme 3: Aldehydes in the Paterno–Büchi reaction.
Scheme 4: 2,3-Diazabicyclo[2.2.1]hept-2-ene (DBH).
Scheme 5: Dissociation pathways of benzaldehyde.
Scheme 6: Reactions that lead to polarized products detectable by CIDNP.
Scheme 7: MMA (26), DEABP (27), and Michler’s ketone (28).
Scheme 8: Radical intermediates of DEABP.
Scheme 9: Photoinitiated polymerization of monomeric MMA (26) using the quinoxalines 32 and benzaldehyde (8).
Scheme 10: Acetone (4) and formaldehyde (35) as photografting initiators.
Scheme 11: Photografting by employing acetaldehyde (36) as the photoinitiator.
Scheme 12: Proposed photolysis mechanism for aliphatic ketones 44 and formaldehyde (35).
Scheme 13: Initiator 50, reductant 51, and benzaldehyde derivatives 52–54 for the polymerization of the methac...
Scheme 14: Proposed mechanism of the photomediated atom transfer radical polymerization employing the benzalde...
Scheme 15: cis/trans isomerization employing triplet states of photosensitizers.
Scheme 16: Salicylaldehyde (68) forms an internal hydrogen bond.
Scheme 17: Olefin isomerization via energy transfer from a carbonyl compound.
Scheme 18: Mechanistic pathways for the Paterno–Büchi reaction.
Scheme 19: Isomeric oxetanes formed after photochemical addition of aryl aldehydes to 2-butenes.
Scheme 20: Rotation of the C3–C4 bond of the biradical intermediate may lead to all four conformations.
Scheme 21: Photolysis products of benzaldehyde (8) in different solvents. a) In benzene or ethanol. b) In hex-...
Scheme 22: N-tert-Butylbenzamide formation proceeds via a benzoyl radical.
Scheme 23: Photochemical pinacol coupling.
Scheme 24: Photochemical ATRA catalyzed by 4-anisaldehyde (52).
Scheme 25: Proposed triplet sensitization mechanism of the ATRA reaction in the presence of 4-anisaldehyde (52...
Scheme 26: Benzaldehyde-mediated photoredox CDC reaction: compatible amides and ethers.
Scheme 27: Photoredox cross-dehydrogenative coupling (CDC) conditions and proposed reaction mechanism.
Scheme 28: Optimized conditions for the photoredox merger reaction.
Scheme 29: Proposed mechanism for the C(sp3)–H alkylation/arylation of ethers.
Scheme 30: Substrate scope for the photochemical alkylation of ethers.
Scheme 31: C(sp3)–H Functionalization of N-containing molecules.
Scheme 32: Substrate scope for the photochemical alkylation of N-containing molecules.
Scheme 33: Additional products yielded by the photochemical alkylation reaction of N-containing molecules.
Scheme 34: C(sp3)–H functionalization of thioethers.
Scheme 35: Proposed mechanism for the C(sp3)–H alkylation/arylation of N-containing molecules and thioethers.
Scheme 36: Hydroacylation using 4-cyanobenzaldehyde (53) as the photoinitiator.
Scheme 37: Selectivity for the formation of the α,α-disubstituted aldehydes.
Scheme 38: Substrate scope for the photochemical addition of aldehydes to Michael acceptors.
Scheme 39: Proposed mechanism for the hydroacylation of Michael acceptors using 4-cyanobenzaldehyde (53) as th...
Scheme 40: Catalytic arylation of aromatic aldehydes by aryl bromides in which the reaction product acts as th...
Scheme 41: Proposed mechanism for the catalytic arylation of benzaldehydes by aryl bromides in which the react...
Scheme 42: Functionalization of the chiral cyclobutanes 180.
Scheme 43: Optimized reaction conditions and proposed mechanism for the sulfonylcyanation of cyclobutenes.
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
- , entries 3–7). In contrast, there is no benefit for the ethylphospholene oxides (1h or 4h) (Table 5, entry 8). The olefinicity concept and the olefinicity value (OL%) was developed to measure and describe quantitatively the degree of conjugation of an alkene group with the neighboring functional groups
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
- of known, in vivo effective substances but also for designing chemically modified analogs as valid alternatives for further therapeutic agents. Keywords: bioactive compounds; enyne metathesis; ring-closing metathesis; ruthenium catalysts; tandem reactions; Introduction Alkene and alkyne metathesis
- potential of enyne metathesis in providing sustainable access to bioactive organic compounds, when used in conjunction with a number of name reactions. Enyne metathesis is a fundamental chemical transformation involving an alkene and an alkyne to produce a dienic structure through unsaturated bond
- the respective dienic compounds (Scheme 2) [52]. The reaction course is essential for directing the process towards the desired exo or endo isomer, in compliance with the required stereochemistry of the final product. For the intermolecular enyne metathesis reaction, the double bond of the alkene is
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
- the Oestreich group in 2016 [27]. The reaction could be performed using CuCN as catalyst in the absence of a ligand. A wide variety of triflates 9, including some containing a remote tosylate, bromide, alkene, or alkyne functionality, afforded the desired alkylsilanes 10–16 in fair to good yields
- also supports a radical mechanism, is depicted in Scheme 7. Here, an intermediate radical could easily be intercepted by a tethered alkene in 30 leading to a 5-exo-trig cyclization and hence, the formation of a 5-membered ring as found in products 31–33. The formation of, e.g., compound 34, suggested
- that a specific geometry of the tethered alkene is required, as no 6-membered ring formation was observed. Interestingly, Cárdenas’ precursor 35 [30] led, after a cascade of reactions, to the formation of compound 36. Computational as well as experimental studies suggested that the ligand and
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.
Design and synthesis of diazine-based panobinostat analogues for HDAC8 inhibition
- Sivaraman Balasubramaniam,
- Sajith Vijayan,
- Liam V. Goldman,
- Xavier A. May,
- Kyra Dodson,
- Sweta Adhikari,
- Fatima Rivas,
- Davita L. Watkins and
- Shana V. Stoddard
Beilstein J. Org. Chem. 2020, 16, 628–637, doi:10.3762/bjoc.16.59
- role of the electronic effects of the nitrogen atoms on this cyclic substrate, and then we revised our synthetic strategy by a) tethering an alkene functional group on the aromatic ring and b) then conducting the oxidation of the benzylic group to afford the aldehyde product. Towards this end, we
Graphical Abstract
Figure 1: Chemical structures of the target diazine-based surrogates for the central core of panobinostat.
Figure 2: Docking pose for panobinostat and panobinostat derivatives in the HDAC8 receptor. (a) Overlay of al...
Figure 3: General building blocks for the visualized targets.
Scheme 1: Reaction conditions: a) MeOH, H2SO4 (5 drops), MS 4 Å (2 pieces), 68 °C, 8 h, 81%; b) DIBAL-H (1.2 ...
Scheme 2: Reaction conditions: a) boronic acid 15 (1.3 equiv), PdCl2(PPh3)2 (0.1 equiv), dioxane/H2O (3:1), Na...
Scheme 3: Reaction conditions: a) 5-bromo-2-chloropyrimidine (1 equiv), ethyl formate (1.5 equiv), THF (20 mL...
Scheme 4: Reaction conditions: a) boronic acid 15 (1.3 equiv), PdCl2(PPh3)2 (0.1 equiv), dioxane/H2O (8:2, Na2...
Controlling alkyne reactivity by means of a copper-catalyzed radical reaction system for the synthesis of functionalized quaternary carbons
- Goki Hirata,
- Yu Yamane,
- Naoya Tsubaki,
- Reina Hara and
- Takashi Nishikata
Beilstein J. Org. Chem. 2020, 16, 502–508, doi:10.3762/bjoc.16.45
- alkene derivatives. Because an alkyne undergoes addition reaction at a C–C triple bond or cross-coupling at a terminal C–H bond. Combining those reaction patterns could realize a new reaction methodology to synthesize complex molecules including C–C multiple bonds. In this report, we found that the
Graphical Abstract
Scheme 1: Reaction modes of alkyne.
Figure 1: Substrate scope of 1 and 2. aConducted at 80 °C for 24 h in MeCN with CuBr (10 mol %), 1,10-Phen (2...
Scheme 2: Proposed mechanism.
Scheme 3: Control experiment.
Scheme 4: Reaction of 2a and 4a.
Figure 2: Substrate scope of 2 and 4. aConducted at 100 °C for 20 h in 1,4-dioxane with CuI (10 mol %), 1,10-...
Recent advances in photocatalyzed reactions using well-defined copper(I) complexes
- Mingbing Zhong,
- Xavier Pannecoucke,
- Philippe Jubault and
- Thomas Poisson
Beilstein J. Org. Chem. 2020, 16, 451–481, doi:10.3762/bjoc.16.42
- subsequently adds to the alkene. The resulting C-centered radical is oxidized by the Cu(II) complex, regenerating the Cu(I) catalyst, and the formed carbocation is trapped by the halide. Worth to mention is that very recently, Reiser and Engl demonstrated the possible use of [Cu(dmp)2Cl]Cl as an efficient
- . When an electron-donating group (e.g., NH, NHCO, and NMe2) was in close proximity to the alkene, the pathway of the addition changed and the chlorotrifluoromethylated adduct was formed. To explain the reaction mechanism, the authors suggested the following pathway: Upon irradiation at 530 nm using
- to the alkene, followed by the addition of SO2Cl to produce the desired product. However, when the reaction rate is slower, the SO2Cl anion decomposes to neutral SO2 and a chloride anion due to the weak nature of the Cu–SO2Cl bond. The SO2 extrusion explains the formation of the
Graphical Abstract
Scheme 1: [Cu(I)(dap)2]Cl-catalyzed ATRA reaction under green light irradiation.
Scheme 2: Photocatalytic allylation of α-haloketones.
Scheme 3: [Cu(I)(dap)2]Cl-photocatalyzed chlorosulfonylation and chlorotrifluoromethylation of alkenes.
Scheme 4: Photocatalytic perfluoroalkylchlorination of electron-deficient alkenes using the Sauvage catalyst.
Scheme 5: Photocatalytic synthesis of fluorinated sultones.
Scheme 6: Photocatalyzed haloperfluoroalkylation of alkenes and alkynes.
Scheme 7: Chlorosulfonylation of alkenes catalyzed by [Cu(I)(dap)2]Cl. aNo Na2CO3 was added. b1 equiv of Na2CO...
Scheme 8: Copper-photocatalyzed reductive allylation of diaryliodonium salts.
Scheme 9: Copper-photocatalyzed azidomethoxylation of olefins.
Scheme 10: Benzylic azidation initiated by [Cu(I)(dap)2]Cl.
Scheme 11: Trifluoromethyl methoxylation of styryl derivatives using [Cu(I)(dap)2]PF6. All redox potentials ar...
Scheme 12: Trifluoromethylation of silyl enol ethers.
Scheme 13: Synthesis of annulated heterocycles upon oxidation with the Sauvage catalyst.
Scheme 14: Oxoazidation of styrene derivatives using [Cu(dap)2]Cl as a precatalyst.
Scheme 15: [Cu(I)(dpp)(binc)]PF6-catalyzed ATRA reaction.
Scheme 16: Allylation reaction of α-bromomalonate catalyzed by [Cu(I)(dpp)(binc)]PF6 following an ATRA mechani...
Scheme 17: Bromo/tribromomethylation reaction using [Cu(I)(dmp)(BINAP)]PF6.
Scheme 18: Chlorotrifluoromethylation of alkenes catalyzed by [Cu(I)(N^N)(xantphos)]PF6.
Scheme 19: Chlorosulfonylation of styrene and alkyne derivatives by ATRA reactions.
Scheme 20: Reduction of aryl and alkyl halides with the complex [Cu(I)(bcp)(DPEPhos)]PF6. aIrradiation was car...
Scheme 21: Meerwein arylation of electron-rich aromatic derivatives and 5-exo-trig cyclization catalyzed by th...
Scheme 22: [Cu(I)(bcp)(DPEPhos)]PF6-photocatalyzed synthesis of alkaloids. aYield over two steps (cyclization ...
Scheme 23: Copper-photocatalyzed decarboxylative amination of NHP esters.
Scheme 24: Photocatalytic decarboxylative alkynylation using [Cu(I)(dq)(binap)]BF4.
Scheme 25: Copper-photocatalyzed alkylation of glycine esters.
Scheme 26: Copper-photocatalyzed borylation of organic halides. aUnder continuous flow conditions.
Scheme 27: Copper-photocatalyzed α-functionalization of alcohols with glycine ester derivatives.
Scheme 28: δ-Functionalization of alcohols using [Cu(I)(dmp)(xantphos)]BF4.
Scheme 29: Photocatalytic synthesis of [5]helicene and phenanthrene.
Scheme 30: Oxidative carbazole synthesis using in situ-formed [Cu(I)(dmp)(xantphos)]BF4.
Scheme 31: Copper-photocatalyzed functionalization of N-aryl tetrahydroisoquinolines.
Scheme 32: Bicyclic lactone synthesis using a copper-photocatalyzed PCET reaction.
Scheme 33: Photocatalytic Pinacol coupling reaction catalyzed by [Cu(I)(pypzs)(BINAP)]BF4. The ligands of the ...
Scheme 34: Azide photosensitization using a Cu-based photocatalyst.
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
- cycle. This type of mechanism has been previously proposed for aryl and alkene alkylations [27][28], but not for direct arylation systems. A possible mechanism is outlined in Scheme 3, informed by the previous reports [27][28][29][30]. The aryl iodide 4 undergoes SET with an excited palladium(0) species
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...
Rapid, two-pot procedure for the synthesis of dihydropyridinones; total synthesis of aza-goniothalamin
- Thomas J. Cogswell,
- Craig S. Donald and
- Rodolfo Marquez
Beilstein J. Org. Chem. 2020, 16, 135–139, doi:10.3762/bjoc.16.15
- and co-workers, who developed a one-pot, three-component reaction to produce protected homoallylic amines 4 (Scheme 1) [19]. It was reasoned that adaptation of the Veenstra protocol would allow us to introduce a second alkene unit during the same process, thus generating a ring-closing metathesis
Graphical Abstract
Figure 1: Aza-goniothalamin 1, (R)-(+)-goniothalamin 2 and acylated aza-goniothalamin analogue 3 [14-18].
Scheme 1: One pot synthesis of benzyl carbamate 4 reported by Veenstra and co-workers [19].
Scheme 2: Formation of diene 5 in 66% through a one pot, three component coupling.
Scheme 3: Optimized conditions for the synthesis of diene 5.
Scheme 4: Ring-closing metathesis reaction of diene 5 to yield dihydropyridone 7 [20-23].
Figure 2: Extension of the two-pot methodology to include a variety of different aldehyde starting materials.
Scheme 5: Total synthesis of aza-goniothalamin 1.
Reversible photoswitching of the DNA-binding properties of styrylquinolizinium derivatives through photochromic [2 + 2] cycloaddition and cycloreversion
- Sarah Kölsch,
- Heiko Ihmels,
- Jochen Mattay,
- Norbert Sewald and
- Brian O. Patrick
Beilstein J. Org. Chem. 2020, 16, 111–124, doi:10.3762/bjoc.16.13
- comparison with literature data [69], and the new compounds 3b and 3d were fully characterized by NMR spectroscopy (1H, 13C, COSY, HSQC, and HMBC), elemental analyses, and mass spectrometry. In all cases, E-configuration of the alkene double bonds in 3a–d was indicated by characteristic coupling constants of
- the alkene protons (3JH–H = 16 Hz) [70]. Absorption and emission properties The photophysical properties of the styrylquinolizinium derivatives 3a and 3c have already been reported [69], while the ones of 3b and 3d were determined in this work (Table 1 and Figure 1). In acetonitrile, the derivatives
- irradiation at λ = 450 nm or λ = 360 nm in acetonitrile, as indicated by the upfield shift of the signals of the alkene double bonds and the characteristic coupling constants of Z-configured protons (3JH–H = 12 Hz). Notably, the derivative 3c did not react any further under these conditions (cf. Supporting
Graphical Abstract
Scheme 1: Synthesis of styrylquinolizinium derivatives 3a–d.
Figure 1: Absorption spectra and normalized emission spectrum (Abs. = 0.10, 3b: λex = 394 nm) of derivatives ...
Figure 2: Spectrophotometric titration upon the addition of ct DNA to the styrylquinolizinium derivatives 3a ...
Figure 3: Spectrofluorimetric titration upon the addition of ct DNA to the styrylquinolizinium derivatives 3a...
Figure 4: CD and LD spectra of the styryl derivatives 3a (A), 3b (B), 3c (C), and 3d (D) with ct DNA in BPE b...
Figure 5: Spectrophotometric monitoring of the irradiation of styrylquinolizinium derivatives 3a (A), 3b (B), ...
Figure 6: Absorption of the monomers (c = 20 µM, red) 3b (A) and 3c (B) and their dimers (black) 4b and 4c in...
Figure 7: Photometric monitoring of the photoreaction of 3b (c = 20 µM) to the dimer 4b by irradiation at ca....
Figure 8: ORTEP drawings of cyclobutane derivatives 4b (A) and 4c (B) in the solid state (thermal ellipsoids ...
Scheme 2: Possible pathways for the selective photodimerization of styrylquinolizinium derivatives 3b and 3c.
Figure 9: A) Spectrophotometric titration of ct DNA to dimer 4b in BPE buffer (cL = 20 µM, cct DNA = 1.45 mM, ...
Figure 10: A) Photometric and B) CD spectroscopic monitoring of the photoinduced switching (4b: λex = 315 nm, ...
Scheme 3: Photoinduced switching of the DNA binding properties of styrylquinolizinium compound 3b.
[1,3]/[1,4]-Sulfur atom migration in β-hydroxyalkylphosphine sulfides
- Katarzyna Włodarczyk,
- Piotr Borowski and
- Marek Stankevič
Beilstein J. Org. Chem. 2020, 16, 88–105, doi:10.3762/bjoc.16.11
- alkene 59 and its transformation to 54. For the reaction performed at 25 °C, the principle observations remained the same except that the reaction speed was remarkably lower. Nevertheless, these experiments allowed to conclude that the rearrangement proceeded via a two-step mechanism, with the first step
- , leading to intermediate I, and the overall transformation proceeded with remarkable stabilization. In the next step, dissociation of the C−O bond occurred through transition state II, finally leading to alkene III. The activation energy for the C−O bond cleavage in 20, a tertiary alcohol, was similar to
- investigated. On the other hand, the complex of 17 and AlCl3 underwent C–O bond cleavage and γ-hydrogen atom abstraction, with an activation barrier of +16.5 kcal/mol, which led to the corresponding alkene, with a stabilization energy of −13.5 kcal/mol. The loss of AlCl3/H2O afforded the β,γ-alkenylphosphine
Graphical Abstract
Scheme 1: Arbusov, phospha-Fries, and phospha-Brook rearrangements.
Scheme 2: Cyclization of 1a and 1b under acidic conditions.
Scheme 3: The synthesis of P-stereogenic β-hydroxyalkylphosphine sulfides.
Scheme 4: Cyclization of 8 and 19 in the presence of H3PO4.
Scheme 5: Cyclization of (SP)-19 in the presence of H3PO4.
Figure 1: 1H NMR spectra of compounds 12 and 29.
Figure 2: 13C NMR spectra of compounds 12 and 29.
Scheme 6: Synthesis of the alkenylphosphine sulfides used in study.
Scheme 7: The reaction of mesylate compounds with Lewis-acidic AlCl3.
Scheme 8: The reaction of alkenylphosphine sulfides with AlCl3.
Scheme 9: Rearrangement of 20 in the presence of Brønsted acid. The calculated energies next to the arrows ar...
Scheme 10: Rearrangement of 20 in the presence of Lewis acid. The calculated energies next to the arrows are r...
Scheme 11: The synthesis of chiral substrates for rearrangement reactions.
Scheme 12: The reaction of (SP)-60 and (SP)-65 with AlCl3.
Scheme 13: Reaction of chiral β-hydroxyalkylphosphine sulfides with Brønsted acid.
Scheme 14: Attempted cyclization of enantiomerically enriched 53 and 46.
Extension of the 5-alkynyluridine side chain via C–C-bond formation in modified organometallic nucleosides using the Nicholas reaction
- Renata Kaczmarek,
- Dariusz Korczyński,
- James R. Green and
- Roman Dembinski
Beilstein J. Org. Chem. 2020, 16, 1–8, doi:10.3762/bjoc.16.1
- confirmed that the Nicholas reaction can be carried out in a nucleoside presence, leading to a divergent synthesis of novel metallo-nucleosides enriched with alkene, arene, arylketo, and heterocyclic functions, in the deoxy and ribo series. Keywords: alkynes; 5-alkynyluridines; C–C-bond formation; dicobalt
- , has been introduced into the repertoire of nucleosides modifications. The reaction of dicobalt hexacarbonyl propargylic alcohol uridine derivatives has been validated with diverse C-nucleophiles. By this means, alkene, arene, arylketo, and heterocyclic functions can be introduced onto metallo
Graphical Abstract
Scheme 1: Preparation of (2'-deoxy)-5-alkynyluridines 2 and 3, their dicobalt hexacarbonyl derivatives 4 and 5...
Figure 1: Structures of nucleosides 6 and 7, products of the Nicholas reaction.
A chiral self-sorting photoresponsive coordination cage based on overcrowded alkenes
- Constantin Stuckhardt,
- Diederik Roke,
- Wojciech Danowski,
- Edwin Otten,
- Sander J. Wezenberg and
- Ben L. Feringa
Beilstein J. Org. Chem. 2019, 15, 2767–2773, doi:10.3762/bjoc.15.268
- between the three isomers. Two of the isomers were able to form host–guest complexes opening up new prospects toward stimuli-controlled substrate binding and release. Keywords: coordination cages; molecular motors; molecular switches; overcrowded alkene; palladium; Introduction Supramolecular
- -pyridinylboronic acid with an E/Z mixture of reported overcrowded alkene precursors [51] (see Supporting Information File 1 for full experimental details). Heating a 2:1 mixture of ligands (S,S)-Z-1 or (S,S)-E-1 with Pd(NO3)2 in acetonitrile at reflux led to the quantitative formation of cage Pd2(stable Z-1)4 or
- (stable E-1)4 generated by irradiation of Pd2(unstable Z-1)4 at 365 nm. Cage formation of overcrowded alkene switches E/Z-1 and their isomerization behavior. Note that the intermediate unstable E-1 is not shown; due to the low barrier of thermal helix inversion and therefore fast isomerization to the
Graphical Abstract
Figure 1: Schematic representation of a photoresponsive cage with ligands based on overcrowded alkenes.
Scheme 1: Cage formation of overcrowded alkene switches E/Z-1 and their isomerization behavior. Note that the...
Figure 2: Aromatic region of stacked 1H NMR spectra (in CD3CN) of stable Z-1 and cage complex Pd2(stable Z-1)4...
Figure 3: HRMS spectra of cage complex Pd2(stable Z-1)4 (top) and cage complex Pd2(stable E-1)4 (bottom); Ins...
Figure 4: Crystal structure of cage complex Pd2(stable E-1)4 (top left) and DFT optimized structures of cage ...
Figure 5: Aromatic region of stacked 1H NMR spectra (CD3CN/CD2Cl2 1:1) of i) Pd2(stable Z-1)4; ii) Pd2(stable ...
AgNTf2-catalyzed formal [3 + 2] cycloaddition of ynamides with unprotected isoxazol-5-amines: efficient access to functionalized 5-amino-1H-pyrrole-3-carboxamide derivatives
- Ziping Cao,
- Jiekun Zhu,
- Li Liu,
- Yuanling Pang,
- Laijin Tian,
- Xuejun Sun and
- Xin Meng
Beilstein J. Org. Chem. 2019, 15, 2623–2630, doi:10.3762/bjoc.15.255
- attacking of nucleophilic partners, followed by a protodemetalation step to form the alkene motif (Scheme 1, path a) [9][10][11]. However, the formation of a silver carbene intermediate, which could be generated usually from relevant diazo precursors [12][13][14], appears to be an unusual event in silver
Graphical Abstract
Scheme 1: Two modes of reactions of alkynes by silver catalysis.
Scheme 2: Reactions of ynamides or ynol ethers with isoxazoles by transition metal catalysis.
Figure 1: Selected bioactive molecules containing the 5-amino-1H-pyrrole-3-carboxamide motif.
Scheme 3: Reactions of ynamide 4a with different isoxazoles 5, 7 and 8a.
Figure 2: Scope with regard to ynamide 4. All reactions were carried out with ynamide 4 (0.2 mmol), isoxazole ...
Figure 3: Scope with regard to the 5-aminoisoxazole 8 (see Figure 2). aReaction conditions: 2.0 equiv of 8e, 100 °C.
Figure 4: Molecular structure in the solid state of compound 10ad.
Scheme 4: A gram-scale experiment.
Scheme 5: Mechanistic hypotheses for Ag-catalyzed reaction of ynamide 4a with aminoisoxazole 8a.
Scheme 6: Possible reaction routes of intermediate C.
