Synthesis of novel 5‐aryl‐6‐cyano‐3 H ,8 H ‐pyrido[2,3‐ d ]pyrimidine‐4,7‐diones in the reaction of 6‐amino‐4‐pyrimidinones with benzaldehyde and ethyl cyanoacetate

The title compounds 4 and 5 have been prepared in one‐step reaction from 6‐amino‐4‐pyrimidinones 1 , the corresponding 4‐substituted benzaldehyde 2 and ethyl cyanoacetate 3 in very good yields. The structure of the final compounds was determined on the basis of nmr measurements, especially by 1 H, 1 H‐, 1 H, 13 C COSY, and DEPT.