AbstractAnthranilonitrile reacts with ethyl isocyanatoacetate to form 2‐(3‐ethoxycarbonylmethylureido)benzonitrile (3b) which, upon heating, or treatment with a base, undergoes a double cyclization to yield imidazo[1,2‐c]‐quinazoline‐2,5‐(3H,6H)dione (5) in excellent yield. In the presence of acid,3bis converted into 1,4‐dihydro‐2,4‐dioxo‐3‐(2H)quinazolineacetic acid (11), or its ethyl ester (10). The action of concentrated sulfuric acid converts the adduct13of anthranilic acid and ethyl isocyanatoacetate into 2‐ethoxycarbonyl‐methylamino‐4H