Synthesis of pyrido[3,2-d]pyrimidines from 5-aminopyrimidines

Abstract

5-Aminouracil, 5-amino-2,4-dimethoxypyrimidine, and 5-amino-1,3-dimethyluracil have been caused to react with αβ-unsaturated aldehydes, ethyl ethoxymethylene-malonate and -cyanoacetate, malonates, and 1,3-dicarbonyl compounds. Certain of the products from these reactions cyclised to yield pyrido[3,2-d]pyrimidines. The ease of cyclisation is shown to depend upon the nature of the substituents in both the aliphatic side-chain and in the pyrimidine ring.