3, 4-Diaminothiophenes (Xa-b) were synthesized by cleavage of the pyridine ring in to 3-aminothien-4-ylpyridinium iodides (Va-d), which were prepared by the reaction of 1-cyanomethylpyridinium chloride with carbon disulfide and alkylating agents (chloroacetonitrile, ethyl bromoacetate, phenacyl bromide, chloroacetamide) in the presence of alkali, followed by base-catalyzed intramolecular cyclization. The reaction of 3, 4-diaminothiophenes with acetic anhydride, benzoyl chloride, and benzaldehydes gave the corresponding products in good yields.
