Trifluoroacetoxysulphenylation of unsaturated nitriles and transformation of the adducts into lactones

Abstract

Reactions of metal acetates with organic disulphides in dichloromethane–trifluoroacetic acid in the presence of unsaturated nitriles give trifluoroacetoxy sulphides, which on hydrolysis readily afford mixtures of the regioisomeric hydroxy sulphides. Optimum yields were obtained with manganese(III)acetate. The mixtures of regioisomeric trifluoroacetoxy sulphides react with acetonitrile under Ritter conditions to give further mixtures of regioisomeric vicinal acetamido sulphides. The regiochemistry of these reactions is discussed. Hydrolysis of the mixtures of trifluoroacetoxy sulphides in aqueous cobalt chloride gives substituted lactones. This high-yield transformation depends upon lactonisation proceeding via an episulphonium ion intermediate; hence conversion of unsaturated nitriles into sulphenyl lactones is characterised by good regiocontrol.