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‐4 H ‐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‐4 H ‐pyrido[3,2‐ e ]‐pyrimido[1,2‐ c ]pyrimidines was performed to give corresponding acid derivatives.