Rearrangements and Fragmentations of Phenyl Styryl Sulfides 2-Labelling studies

Article abstract of DOI:10.1002/oms.1210170907

Metastable molecular ions of phenyl styryl sulfides may decompose by loss of CH3^., SH^., CHS^., C6H5^., C6H6 or C7H7^..Labelling with carbon-13 and deuterium gave information about the mechanisms of these reactions.It appears that extensive rearrangements occur prior to most of these fragmentations.In the case of phenyl β-styryl sulfide both phenyl groups and both vinyl carbon atoms are found in the C7H7 fragment in comparable amounts.For phenyl α-styryl sulfide this fragmentation leads more specifically to the loss of the S-phenyl group and the β-vinyl carbon atom.It was concluded that rearrangements occur, partly via symmetric diphenyl ethene sulfide structures, to benzyl phenyl thione ions, from which the fragmentation occurs.For the loss of CHS^. an earlier proposed mechanism was confirmed.From both compounds the S-phenyl ring can be lost as C6H5^. or C6H6 as well as the C-phenyl ring.Fragmentation occurs from one of the initial structures as well as from benzyl phenyl thione.Loss of CH3^. is thought to occur after ring closure with formation of dihydrobenzothiophenes followed by ring opening by rupture of a C-S bond.While phenyl β-styryl sulfide shows a strong tendency towards isomerization to a symmetric structure like 1,2-diphenylethene sulfide, phenyl α-styryl sulfide easily rearranges in an electrocyclic reaction with formation of benzyl phenyl thione.