Control of regioselectivity in the addition of sulphenyl chlorides to 3,3-dimethylbutyne (t-butylacetylene) as a method for differential functionalization of triple bonds

Abstract

Methanesulphenyl chloride and toluene-p-sulphenyl chloride react with 3,3-dimethylbutyne to give regio- and stereo-specifically (E)-1-chloro-3,3-dimethyl-2-methylthiobut-1-ene (3a) and (E)-1-chloro-3,3-dimethyl-2-p-tolylthiobut-1-ene (3b). trans–cis-Acid-catalysed isomerization of (3a) and (3b) may occur. Sulphenyl chlorides catalyse the conversion of (3a) and (3b) into (Z)-2-chloro-3,3-dimethyl-1-methylthiobutene (4a) and (Z)-2-chloro-3,3-dimethyl-1-p-tolylthiobutene (4b) respectively. The hydrolysis of compounds (3) and (4) affords 1-chloro-3,3-dimethylbutan-2-one (5) and 2-chloro-3,3-dimethylbutanal (6).