Synthesis of 2‐amino‐4‐imino‐4,5‐dihydrothiazoles from N‐sulfonyl‐α‐chloroamidines and thiourea

Abstract

A number of new and interesting 2‐amino‐4‐(N‐substituted)imino‐4,5‐dihydrothiazoles were synthesized by reacting thiourea (or thiourea hydrochloride) with N‐alkyl‐ or N,N‐dialkyl‐N′‐p‐toluenesulfonyl‐α‐chloroacetamidines, where the N,N‐alkyl groups were ethyl, cyclohexyl, benzyl, β‐phenethyl, (3,5‐dimethyl‐1‐adamantyl)‐methyl, as well as N,N‐dimethyl‐ and N,N‐pentamethylene. Reactions of N‐alkyl‐N‐p‐toluenesulfonyl‐2‐chloroacetamidines (substituents being N‐ethyl, N‐benzyl and N,N‐dimethyl) with thiourea hydrochloride in hot 2‐propanol furnished 2‐amino‐4‐(p‐toluenesulfonyl)imino‐4,5‐dihydrothiazole (in 51, 60 and 65% yields, respectively) and the corresponding amine hydrochloride. In hot acetone or butanone, the reactions of these N‐sulfonyl‐2‐chloroacetamidines with excess thiourea provided 2‐amino‐4‐N‐(alkyl or N,N‐dialkyl)imminium‐4,5‐dihydrothiazole chlorides in 25–80% yield. The by‐product from these reactions was p‐toluenesulfonamide. The structures of the products were established by chemical transformations and spectral methods (nmr and mass spectra).