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‐pyrido[3,2‐e]pyrimido[1,2‐c]pyrimidines from 4‐aminopyrido[2,3‐d]pyrim‐idines 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.