Starting from 4,5-dihydro-4-imino-6-(methylthio)-N,5-diphenylisothiazolo[3,4-d] pyrimidin-3-amin (1), synthetic pathway to 6-Hydrazinyl-4, 5-dihydro-4-imino-N,5-diphenylisothiazolo[3,4-d]pyrimidin-3-amine (2) is described. The reaction of 4 ,5-dihydro-4-imino-6-(methylthio)-N,5-diphenylisothiazolo[3,4-d]pyrimidin-3-amin (1) with hydrazine hydrate afforded the corresponding hydrazino derivatives (2). Further treatment of these compounds with different orthoesters in acetic acid gave the corresponding N-(4-imino-8-alkyl-5-phenyl-4,5-dihydro[1,2,4]triazolo[3',4':2,3] pyrimido[4,5-c]isothiazolo-3-yl) N-phenylamine (3a-c). Reaction of 6-Hydrazinyl-4, 5-dihydro-4-imino-N,5-diphenylisothiazolo[3,4-d]pyrimidin-3-amine (2) with carbon disulphide afforded the Anilino-4-imino-5-phenyl-4,5,7,8-tetrahydro[1,2,4] triazolo [3',4':2,3]pyrimido[4,5-c] isothiazolo -8-thione (4).

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