THIOL ADDITIONS TO 1,4-DIARYLSULFONYL-2-BUTYNES. STEREOCHEMISTRY OF ADDITION AND REGIOSPECIFIC ELIMINATIONS FROM THE ADDUCTS

Abstract
Thiol additions to 1,4-diarylsulfonyl-2-butynes result in stereoselective formation of 1,4-diarylsulfonyl-2-arylthio-2-butenes with a preponderance of the E isomer over the Z. Contrary to the behaviour of similar adducts from 1-arylsulfonyl-4-(N′-anilino)-2-butynes and 1-arylsulfonyl-4-arylthio-2-butynes, the vinyl sulfides obtained from the diarylsulfonylbutynes undergo facile isomerization under mild base catalysis. A regiospecific elimination followed by readdition is shown to be the mechanism for such isomerizations.