Thioxopyrimidine in Heterocyclic Synthesis II: Novel Synthesis of Some Triazoles and Triazepine Derivatives with a Pyrimido[3,2:4,5]thieno[2,3‐d]pyrimidine Skeleton

Abstract

Condensation of ethoxymethyleneamino‐thieno[2,3‐d]pyrimidines 4 with appropriate amino compounds afforded the corresponding 7‐substituted‐8‐imino‐pyrimido[3,2:4,5]thieno[2,3‐d]pyrimidines 6a, 6b, and 7 and 2‐substituted‐pyrimido[3′,2′:4,5]thieno[3,2‐e][1,2,4]triazolo[1,5‐c]pyrimidines 9a, 9b, respectively. Also, hydrazinolysis of compound 4 in ethanol which yielded the key intermediate 7‐amino‐8‐imino‐pyrimido[3,2:4,5]thieno[2,3‐d]pyrimidine (10), which can be cyclized with appropriate isothiocyanates 14a–14g in refluxing pyridine, afforded the corresponding 2‐(substituted‐amino)‐pyrimido[3′,2′:4,5]thieno[3,2‐e][1,2,4]triazolo[1,5‐c]pyramidines 15a–15g. Furthermore, intramolecular cyclization of compound (10) with appropriate 1,3‐dibromopropane and Mannich bases 18a–18c under the basic condition afforded the corresponding (tri)dihydropyrimido[3′,2′:4,5]thieno[3,2:4,5]pyrimido[1,6‐b][1,2,4]triazepines 16 and 18a–18c, respectively. On the other hand, the 11‐substituted‐pyrimido[3′,2′:4,5]thieno[3,2:4,5]pyrimido[1,6‐b][1,2,4]triazepines 21a–21e were also obtained by the intramolecular cyclization of compound (10) with appropriate enaminone derivatives 19a–19e under the acidic condition.