The chemistry of polyazaheterocyclic compounds. Part VI. Condensation reactions of 5-amino-1H-1,2,3-triazoles with ethyl acetoacetate and a new type of dimroth rearrangement

Abstract

Condensation of 5-amino-4-phenyl-1H-1,2,3-triazole (4a) with ethyl acetoacetate in the presence of piperidine affords mainly 5-methyl-3-phenyl-v-triazolo[3,4-a]pyrimidin-7(4H)-one (9a). which is also the major product of the piperidine-catalysed cyclisation of the triazole derivatives (5a) and (7a). The isomer (10a) was only a minor product of these reactions. In contrast, heating a mixture of the annino-1,2,3-triazolecarbpxamide (4c) and ethyl acetoacetate, or the vinylaminotriazole (5c) with piperidine in ethanol affords an inseparable mixture of the isomeric v-triazolo[3,4-a]pyrimidinecarboxamides (9b) and (10b). The thermal conversion of the v-tri-azolopyrimidine (9a) into the isomer (10a) and its re-formation from the latter by heating with piperidine in ethanol constitutes a new type of reversible Dimroth rearrangement. The course of the reactions are discussed.