INTRAMOLECULAR TRAPPING REACTIONS OF VINYLSULFENIC ACID TAUTOMERS OF ENETHIOLISABLE SULFINES

Thermal intramolecular cyclisation of enethiolisable (allylsulfanyl)su lfines affords 2-alkylidene-1,3-dithiolane 1-oxides in good yields. Th e formation of these compounds is explained by an initial tautomerisat ion of the sulfine to vinylsulfenic acid, followed by an intramolecula r addition of the sulfenic acid to the allylic double bond. Also, sulf ines having an S-(prop-2-ynyl) substituent have been investigated and they similarly give 2-alkylidene-5-methylene-1,3-dithiolane 1-oxides. The results obtained by using thionyl chloride to promote the reaction turned out to be highly dependent upon the structure of the starting sulfine.