Intramolecular trapping reactions of vinylsulfenic acid tautomers of enethiolisable sulfines
Thermal Intramolecular cyclisation of enethiolisable (allylsulfanyl)sulfines affords 2-alkylidene-1, 3-dithiolane 1-oxides in good yields. The formation of these compounds is explained by an initial tautomerisation of the sulfine to vinylsulfenic acid, followed by an Intramolecular addition of the sulfenic acid to the allylic double bond. Also, sulfines 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.