KEYWORDSIn the reaction of 2-amino-3-carbethoxythiophene derivative 2b with hydrazine hydrate the respective aminocarbohydrazide 3 was isolated. Treatment of the latter product with carbon disulfide in alkaline medium caused a heterocyclization to give 1,3,4-oxadiazole-2-thione 5 rather than 3-amino-2-thioxothieno[2,3-d]pyrimidin-4-one 4, which could be obtained on treatment of carbohydrazide 3 with thiourea. The structure of products 4 and 5 was proved by spectroscopic methods and chemical transformations. D… Show more
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