Cycloaddition‐elimination reactions of 4‐methyl‐5‐phenylimino‐Δ 2 ‐1,2,3,4‐thiatriazoline with electrophilic nitriles

4‐Methyl‐5‐phenyliminothiatriazoline 4 undergoes two consecutive cycloaddition‐elimination reactions with ethyl cyanoformate and p ‐toluenesulfonyl cyanide in refluxing chloroform, and yields the 1,2,4‐thiadiazolines 6a,b via the isomers 5a,b . In acetone as the solvent, the reactions occur at room temperature, due to the formation of the 1,2,4‐oxathiazolidine 12 as the intermediate. When trichloroacetonitrile was used, only the decomposition products of 4 , namely 7 and 8 were obtained.