acetal like nature of carbon-5-in 5-aryl-4,5-dihydro-3-methoxycarbonyl isothiazolo [4,3-d] pyrimidine-7 [6H] -one

ABSTRACT

Hydrazinolysis of 5-substituted 4,5- dihydro-3-ethoxy carbonylisothiazolo [4,3-d] pyrimidine-7 [6H]-one derivatives [Ia-h] causes dihydropyrimidinone ring opening and formation of 4-amino-3-carbamoyl-5-hydrazinocarbonylisothiazole [II]. A rational for the case of the dihydropyrimidinone ring opening in such compounds by hydrazine and a plausible mechanism for the reaction were presented. An alternative route for the preparation of 5-aryl-4,5-dihydro -3-arylidenehydrazinocarbonylisothiazolo [4,3-d] pyrimidine-7 [6H]-one derivatives [VIIa-h] was given