An unusually easy [1,3]-migration of the PhS group in 3-methyl-4-phenylthiohept-2-en-1-ols

Hydride reduction of the 2(Z)- and 2(E)-isomers of methyl and tert-butyl 3-methyl-4-phenylthioheptenoates under standard conditions is accompanied by [1,3]-migration of the PhS group and in both cases (E)-3-methyl-2-phenylthiohept-3-en-1-ol 5 is produced, whose structure is confirmed by spectroscopic methods, instead of the expected (Z)-3-methyl-4-phenylthiohept-2- 3a and (E)-2-enol 3b; compounds 3a,b obtained under specially developed conditions undergo isomerisation to compound 5 during chromatography on SiO₂ or on storage in the light of their solutions in CDCl₃ or in C₆D₆.