35181-78-3Relevant academic research and scientific papers
Reaction of Diphenyl Disulfide with Alkynes Promoted by Di-tert-butyl and Dibenzoyl Peroxides: a Useful Syntheic Route to 3- (and 2,3) Substituted Benzothiophenes
Benati, Luisa,Montevecchi, Pier Carlo,Spagnolo, Piero
, p. 1659 - 1664 (2007/10/02)
Thermal reactions of diphenyl disulfide 1 with phenylacetylenes 2a-e promoted by di-tert-butyl peroxide (TBP) at 110 or 150 deg C provides a useful synthetic route to the (2-substituted) 3-phenylbenzothiophenes 4a-e, which result from intramolecular cyclization of 1-phenyl-2-(phenylthio)vinyl radical intermediates 3a-e.Similar reactions of the disulfide 1 with tert-butyl- and trimethylsilylacetylenes 2f and 2g also provide the corresponding benzothiophenes 4f and 4g in satisfactory yields; low yields of the benzothiophene products 4h, i, however, are obtained with hex-1-yne 1h and hex-3-yne 1i.Evidence is presented that the thermal reaction of the disulfide 1 with the alkynes 2 at 100 deg C in the presence of dibenzoyl peroxide, while being of little use for the synthesis of benzothiophenes 4, generally leads to the 2-(phenylthio)vinyl benzoates 10; this is ascribed to initial addition of benzoyloxy radicals to alkyne triple bonds.
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.
