- Selectivity control in thiol-yne click reactions: Via visible light induced associative electron upconversion
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An associative electron upconversion is proposed as a key step determining the selectivity of thiol-yne coupling. The developed synthetic approach provided an efficient tool to access a comprehensive range of products-four types of vinyl sulfides were prepared in high yields and selectivity. We report practically important transition-metal-free regioselective thiol-yne addition and formation of the demanding Markovnikov-type product by a radical photoredox process. The photochemical process was directly monitored by mass-spectrometry in a specially designed ESI-MS device with green laser excitation in the spray chamber. The proposed reaction mechanism is supported by experiments and DFT calculations. This journal is
- Ananikov, Valentine P.,Burykina, Julia V.,Gordeev, Evgeniy G.,K?nig, Burkhard,Shlapakov, Nikita S.
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p. 10061 - 10070
(2020/10/13)
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- Free-Radical Reactions of Benzenethiol and Diphenyl Disulphide with Alkynes. Chemical Reactivity of Intermediate 2-(Phenylthio)vinyl Radicals
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Reaction of benzenethiol at 100 deg C with neat alkyl- and dialkyl-acetylenes leads to virtually quantitative formation of isomeric mixtures of (E)- and (Z)-vinyl sulphide adducts in ratios which depend largely upon both the extent and the nature of alkyl substitution.Results are explained in terms of rapidly interconverting sp2-hybridized (E)- and (Z)-1-alkyl-2-(phenylthio)vinyl radical intermediates which can undergo hydrogen transfer from benzenethiol to an extent which is essentially dependent upon the steric hindrance of their cis-2-substituent.Consistent results are provided by related radical reactions of diphenyl disulphide with alkyl-substituted alkynes to afford varying amounts of 1,2-bis(phenylthio)ethylene adducts ascribable to SH2 reaction of the resulting 1-alkyl-2-(phenylthio)vinyl radicals with the disulphide present.Under analogous conditions benzenethiol and diphenyl disulphide react with phenylacetylenes to give vinyl sulphide or bissulphide adducts in a trans-stereoselective fashio.The findings are interpreted by suggesting, for the intermediate sp-hybridized 1-phenyl-2-(phenylthio)vinyl radicals, the occurrence of significant bonding interaction between the unpaired electron and the adjacent sulphur, which would essentially prevent attack of radical scavenger on the side cis to PhS.Evidence is also presented that 1-phenyl-2-(phenylthio)vinyl radicals can exhibit homolytic intramolecular cyclization reactions, leading to benzothiophene products to a comparatively much greater extent than the 1-alkyl-2-substituted analogues; however, 1-tert-butyl-2-(phenylthio)vinyl radical would represent a special case.
- Benati, Luisa,Montevecchi, Pier Carlo,Spagnolo, Piero
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p. 2103 - 2109
(2007/10/02)
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- Boron Trifluoride-promoted Reaction of 4'-Nitrobenzenesulphenanilide with Alkynes. Formal Addition of Benzenesulphenyl Fluoride to Carbon-Carbon Triple Bonds
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The BF3-promoted reaction of 4'-nitrobenzenesulphenanilide with simple alkyl- and aryl-alkynes at 80 deg C in the presence of tetrabutylammonium tetrafluoroborate provides a one-pot synthetic route to β-fluorovinyl sulphides via a formal regioselective and trans-stereospecific addition of benzenesulphenyl fluoride towards carbon-carbon triple bonds.
- Benati, Luisa,Montevecchi, P. Carlo,Spagnolo, Piero
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p. 1690 - 1695
(2007/10/02)
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- ELECTROPHILIC ADDITION OF 4'-NITROBENZENESULPHENANILIDE TO ALKYNES, EFFECTS OF ARYL AND ALKYL SUBSTITUENTS AT RING CARBONS OF INTERMEDIATE THIIRENIUM IONS
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The BF3-promoted addition of 4'-nitrobenzenesulphenanilide, NBSA, to a number of aryl- and alkyl-acetylenes has been investigated in dichloromethane, p-xylene and/or benzene.Diphenylacetylene, 1a, 1-phenylbutyne, 1b, and 1-phenylpropyne, 1c, generally lead to 1,2-bis(phenylthio)alkenes 4a-c, and N-(4-nitrophenyl)-S-phenyl-S-(2-phenylthiovinyl)sulphimides, 6a-c, in fair to good yields with trans stereospecificity.Phenylacetylene, 1d, similarly gives the corresponding bis(phenylthio)adduct 4d and sulphimide 6d in dichloromethane, but in the aromatic solvents these products are essentially suppressed in favour of 1-aryl-1-phenyl-2-(phenylthio)ethylenes 7d.On the other hand, alkyl- and, particularly, dialkyl-substituted acetylenes preferentially afford β-fluorovinyl sulphides, 5, with trans stereospecifity.These findings are interpreted in terms of a different reactivity towards nucleophilic attack of the intermediate aryl- and alkyl-trihirenium ions which would result from electrophilic sulphenylation of the corresponding alkynes.Steric effects of the substituents are believed to play a major role in determining the different reactivity observed.
- Benati, Luisa,Montevecchi, Pier Carlo,Spagnolo, Piero
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p. 609 - 616
(2007/10/02)
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- Phenylthio Migrations in Rearrangements of 2,2-Bisphenylthioethanols
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Thionyl chloride causes rearrangement of the title compounds to give 2,3-bisphenylthiopropenes (12) by a phenylthio shift.The products undergo phenylthio shifts on exposure to light.Some applications to synthesis are described.
- Blatcher, Philip,Warren, Stuart
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p. 1055 - 1066
(2007/10/02)
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