Studies on Heterocyclic Compounds. XII. A Novel Synthesis of 5-Oxo- and 7-Oxo-pyrido [2, 3-d] pyrimidines

Abstract

A simple synthesis of pyrido [2, 3-d] pyrimidine derivatives as an antitumor agent was reported. Reaction of 6-amino- and 6-(substituted) amino-1, 3-dimethyluracil (I) with dimethyl acetylenedicarboxylate in methanol afforded a mixture of 5-oxo- and 7-oxopyrido-[2, 3-d] pyrimidines and an open-chain intermediate. This intermediate was proved to be 5-substituted 6-aminopyrimidine (VIa), and to be cyclized to 7-oxopyrido [2, 3-d] pyrimidine (VIIIa). On the other hand, 5-oxo compounds were obtained from the reaction of I with diketene or ethyl acetoacetate.