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,ll-disubstituted-4-oxo-4H-pyrido3,2-e]pyrimido1,2-c]pyrimidines from 4-aminopyrido2,3-d]pyrim-idines via thermal cyclization of the intermediate ethyl 2-carbethoxy-3-5,7-disubstituted-4-amino-pyrido2,3-d]pyrimidin-4-yl]acrylates. The alkaline hydrolysis of 3-carbethoxy-4-oxo-4H-pyrido3,2-e]-pyrimido1,2-c]pyrimidines was performed to give corresponding acid derivatives.