Diethyl ethoxymethylenemalonate in triheterocycles: A new synthesis of pyrido[3,2-e]pyrimido[1,2-c]pyrimidines

Diethyl ethoxymethylenemalonate was used for the novel synthesis of the triheterocyclic 3-carbethoxy-9, 11-disubstituted-4-oxo-4H-pyrido[3,2-e]pyrimido[1,2-c]pyrimidines from 4-aminopyrido[2,3-d]pyrimidines via thermal cyclization of the intermediate ethyl 2-carbethoxy-3-[5,7-disubstituted-4-amino-pyrido[2,3-d]pyrimidin-4-yl]acrylates. The alkaline hydrolysis of 3-carbethoxy-4-oxo-4H-pyrido[3,2-e]pyrimido[1,2-c]pyrimidines was performed to give corresponding acid derivatives.