Methyl 2‐benzoylamino‐3‐dimethylaminopropenoate in the synthesis of heterocyclic systems. An attempt to prepare benzoylamino substituted azolo‐ and azinopyrimidines with a bridgehead nitrogen atom

Methyl 2‐benzoylamino‐3‐dimethylaminopropenoate (2) was introduced as a new reagent for the preparation of fused pyrimidinones 4 from heterocyclic α‐amino compounds in acetic acid. In this manner, derivatives of pyrido[1,2‐a]pyrimidine 4a,b,f, pyrimido[1,2‐b]pyridazine 4g, pyrimido[1,2‐c]pyrimidine 4j, pyrazino[1,2‐a]pyrimidine 4k, thiazolo[2,3‐b]pyrimidine 41, pyrazolo[1,5‐a]pyrimidine 4m, and 1,2,4‐triazolo‐[1,5‐a]pyrimidine 4n were prepared.