Synthesis of 4,7-Diaryl-3,4-dihydropyrido[4,3-d]pyrimidin-2(1H)-ones

Preparative methods were developed for the synthesis of 4,7-diaryl-3,4-dihydropyrido[4,3-d]pyrimidin-2(1H)-ones based on readily available Biginelli products. Optimal conditions for the reaction of 4-aryl-6-styryltetrahydropyrimidine-5-carbaldehydes with ammonium salts were selected, enabling the preparation of substituted pyrido[4,3-d]pyrimidinones in yields up to 57%. An alternative synthetic route involving oxime formation followed by cyclization under the action of DBU was also studied.