Cycloaddition reactions of 1,4,2-dithiazole-5-thiones
Abstract
1,4,2-Dithiazole-5-thiones can act either as the 2-atom or the 3-atom component in 2 + 3-cycloadditions. Benzonitrile N-phenylimine, generated in situ by dehydrochlorination of N-phenylbenzohydrazonoyl chloride, reacts at the exocyclic CS double bond forming the thiadiazolethione (17) and the spiro compound (18) by collapse of the initial cycloadduct (19) and further 1,3-dipolar cycloaddition. The corresponding reaction with ethyl azidoformate yields a 5-ethoxycarbonylimino-1,4,2-dithiazole. On treatment with dimethyl acetylenedicarboxylate and ethyl cyanoformate the dithiazolethione itself acts as a 1,3-dipole forming 1,3-dithiole and 1,4,2-dithiazole thiones with expulsion of a nitrile fragment.