Synthesis of 6‐aryl‐1,3‐dimethyl‐6,7‐dihydro‐6‐azalumazin‐7‐(6 H )ones and their conversion into 2‐aryl‐1,2,4‐triazine‐3,5‐(2 H ,4 H )odiones. A new synthesis of 1‐aryl‐6‐azauracils

Treatment of 6‐amino‐5‐arylazo‐1,3‐dimethyluracils with urea or N,N ′‐carbonyldiimidazole gave the respective 6‐aryl‐1,3‐dimethyl‐6,7‐dihydro‐6‐azalumazin‐7‐(6 H )ones, which were hydrolyzed with alkali to afford 2‐aryl‐2,3,4,5‐tetrahydro‐3,5‐dioxo‐1,2,4‐triazine‐6‐carboxylic acids (1‐aryl‐6‐azauracil‐5‐carboxylic acids). Thermal decomposition of these carboxylic acids gave the corresponding 2‐aryl‐1,2,4‐triazine‐3,5‐(2 H ,4 H )diones (1‐aryl‐6‐azauracils). Methylation of the latter with methyl iodide gave the corresponding 2‐aryl‐4‐methyl‐1,2,4‐triazine‐3,5‐(2 H ,4 H )diones (1‐aryl‐3‐methyl‐6‐azauracils).