Efficient synthesis of phosphorylated ortho-fused azaheterocycles

A simple and efficient two-step synthesis of various ortho-fused azaheterocycles, containing phosphorylated pyrimidinones as a parent component, was accomplished by the reaction of 2-diethoxyphosphoryl-3-methoxyacrylate with heteroaromatic amines followed by intramolecular N-acylation of the obtained substitution products. Optimization studies performed for the N-acylation reaction revealed that heating the addition products in Dowtherm A at 250 °C gave the best results. The same conditions applied in the intramolecular cyclization of ethyl 2-diethoxyphosphoryl-3-aminophenylacrylate gave expected product of the electrophilic aromatic substitution, but in low yield.