Formation and Reactions of (1-Chloroalkyl)carbamoyl Chlorides. Synthesis of 1,2,4-Triazolidine-5-ones

N-(α-Chlorobenzyl)carbaniloyl chloride and (α-chlorobenzyl)methylcarbamoyl chloride are formed by reaction of phosgene with N-benzylideneaniline and N-benzylidenemethylamine, respectively. Reaction of these carbamoyl chlorides with a number of nucleophiles is described, some of which cause cleavage of the benzyl to nitrogen bond while others give rise to substitution products without such cleavage. Of the latter type, substituted hydrazines react to effect ring closure to1,2,4-triazolidine-5-ones. The method serves as a convenient synthesis of these new heterocyclic systems.