N-Quaternary compounds. Part 53. Vinylation reactions of pyridine-2-thiones

Abstract

N-Vinyl derivatives of pyridine-2-thiones can be prepared by initial synthesis of dihydrothiazolo[3,2-a]pyridinium derivatives which are ring-opened by a strong base such as potassium t-butoxide in dimethylformamids The product ratios of the separable N- and S-vinyl isomers formed depend largely on the nature and positions of their substituents. The major pathways in the ring-opening reactions of the dihydrothiazolo[2,3-a]pyridinium intermediates have been elucidated by deuterium labelling experiments. Syntheses of a number of selectively deuteriated compounds are described.