Halogenation of Thioamides

The reaction of thioamides with suitable chlorinating agents, such as phosphorus halides, thionyl chloride, carbonyl chloride, etc., is perhaps the most general method of synthesis of imidoyl chlorides. However, this method has been used only in very few instances because thioamides are less readily available than amides. 

For example, Dimroth treated thioamides, derived from isothiocyanates and malonates, with phosphorus pentachloride, and he obtained the corresponding imidoyl chlorides (III), which can be dehydro-chlorinated to produce the ketenimines IV. 

Halogenation of N-alkyl thiobenzamide with elementary chlorine similarly yields the corresponding imidoyl chlorides. For example, from N-methylthiobenzamide (VX methylbenzimidoyl chloride (VI) was obtained ( ). 

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