Pyrimidines. LII Synthesis of pyrido[2,3-d]pyrimidine-2,4-diones and pyrido[2,3-d:6,5-d']dipyrimidine-2,4,6,8-tetrones

Reactivities of 5-dimethylaminomethylene-6-imino-1,3-dimethyluracil hydrochloride ( 1 ) toward a variety of active methylene compounds 2 and 5 were investigated. Treatment of 1 with active methylene compounds such as malononitrile and ethyl cyanoacetate in the presence of triethylamine gave pyrido2,3-d]pyrimidine-2,4-dione derivatives 3. Reaction of 1 with barbituric acids resulted in the formation of pyrido2,3-d:6,5-d′]di-pyrimidine-2,4,6,8-tetrone derivatives 6.