Synthesis of new 5-aryl pyrido [3', 2': 4, 5] thieno [2, 3-e] [1, 2, 3, 4] tetrazolo [1, 5-c] pyrimidine derivatives

Abstract

Few pyrido [3', 2': 4, 5] thieno [2, 3-e][1, 2, 3, 4] tetrazolo [1, 5-c] pyrimidines are $known^{1-4}$ but, to the best of our knowledge, none of their 5-aryl derivatives has been reported in the literature. The routes to these compounds are limited and start from suitably substituted pyridothienopyrimidines either through diazotization of their hydrazino derivative with sodiumn itrite in acetic $acid^{1,4}$ or by the reaction of their chloro compound with sodium azide in ethanol or $acetonitrile^{1,3,4}$ In connection with our interest in the chemistry of fused thienopyridines, we reported a convenient synthesis of pyrido [3', 2': 4, 5] thieno [3, 2-d] pyrimidine-4(3H)-ones from ethyl-3-amino [2, 3-b] pyridine-2 carboxylate through heterocyclization with aryl $nitriles.^5$ In continuation of this work and due to our interest in the synthesis of fused $heterocycles^{5-13}$ we report herein a facile one-step synthesis of new 5-arylpyridothieno tetrazolopyrimidine derivatives (2a-f ).