98805-81-3Relevant articles and documents
Free-Radical Reactions of Benzenethiol and Diphenyl Disulphide with Alkynes. Chemical Reactivity of Intermediate 2-(Phenylthio)vinyl Radicals
Benati, Luisa,Montevecchi, Pier Carlo,Spagnolo, Piero
, p. 2103 - 2109 (2007/10/02)
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.
ELECTROPHILIC ADDITION OF 4'-NITROBENZENESULPHENANILIDE TO ALKYNES, EFFECTS OF ARYL AND ALKYL SUBSTITUENTS AT RING CARBONS OF INTERMEDIATE THIIRENIUM IONS
Benati, Luisa,Montevecchi, Pier Carlo,Spagnolo, Piero
, p. 609 - 616 (2007/10/02)
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.
