Synthesis of Oxazolo[5,4‐d][1,2,4]triazolo[4,3‐a]pyrimidines as a New Class of Heterocyclic Compounds

Abstract

Several new derivatives of oxazolo[5,4‐d]pyrimidine (3a, 3b, 3c, 3d, 3e, 3f, 3g, 3h) have been synthesized through the reaction of 2,4‐dichloro‐6‐methyl‐5‐nitropyrimidine (2) with aryl carboxylic acids in refluxing POCl3. Further treatment of compounds (3a, 3b, 3c, 3d, 3e, 3f, 3g, 3h) with hydrazine hydrate gave the hydrazine derivatives (4a, 4b, 4c, 4d, 4e, 4f, 4g, 4h) that were subsequently cyclized into a novel heterocyclic system, oxazolo[5,4‐d][1,2,4]triazolo[4,3‐a]pyrimidine (5a, 5b, 5c, 5d, 5e, 5f, 5g, 5h, 5i, 5j, 5k, 5l, 5m, 5n, 5o, 5p) and (7a, 7b, 7c, 7d) on treatment with triethylorthoesters or carbondisulfide and alkylhalides, respectively.