Alkyl ( E,Z )‐2‐(2‐benzoyl‐2‐ethoxycarbonyl‐1‐ethenyl)amino‐3‐dimethylaminopropenoates in the synthesis of fused pyrimidinones. A facile route to 3‐aminoazino‐4 H ‐pyrimidin‐4‐ones

Alkyl ( E ,Z)‐2‐(2‐benzoyl‐2‐ethoxycarbonyl‐1‐ethenyl)amino‐3‐dimethylaminopropenoates 1a,b react with het‐eroarylamines 2 to give alkyl 2‐(2‐benzoyl‐2‐ethoxycarbonyl‐1‐ethenyl)amino‐3‐heteroarylaminopropenoates 3‐13 . These were cyclized into fused 3‐(2‐benzoyl‐2‐ethoxycarbonyl‐1‐ethenyl)amino‐4 H ‐azolo‐ (or azino)‐pyrim‐idin‐4‐ones 14‐18 . 2‐Benzoyl‐2‐ethoxycarbonyl‐1‐ethenyl group can be easily removed from 3‐(2‐benzoyl‐2‐ethoxycarbonyl‐1‐emenyl)amino‐8‐memyl‐4 H ‐pyrido[1,2‐ a ]pyrimidin‐4‐one ( 14 ) to give 3‐amino‐8‐methyl‐4 H ‐pyrido[1,2‐a]pyrimidin‐4‐one ( 19 ). The structure of 1a was confirmed by X‐ray analysis.