A new entry to the imidazo[4,5‐ d ]pyrimidine system. The reaction of 1,3‐dimethyl‐6‐aminouracil with N,N ‐dimethyldichloromethyleniminium chloride (phosgeniminium chloride) and trimethylsilyl azide, a novel and convenient “one pot” synthesis of 8‐ N ‐arylaminotheophyllines (2‐ N ‐arylamino‐4,6‐dimethylimidazo[4,5‐ d ]pyrimidine‐(4H,6H)‐5,7‐diones), starting from 1,3‐dimethyl‐6‐aminouracil

1,3‐Dimethyl‐6‐aminouracil 2 was converted into various 8‐ N ‐arylaminotheophyllines (2‐ N ‐arylamino‐4,6‐dimethylimidazo[4,5‐ d ]pyrimidine‐(4 H ,6 H )‐5,7‐diones) 17 through reaction successively, with phosgeniminium chloride ( N,N ‐dimethyldichloromethyleniminium chloride) ( 1a ), trimethylsilyl azide ( 4 ) and arylamines. Starting with the synthesis of the N,N ‐dimethyl(1,3‐dimethyl‐4‐aminouracil‐5‐yl)chloromethyleniminium chloride (amide chloride) 3 this new route to the imidazo[4,5‐ d ]pyrimidine skeleton was shown to proceed via the formation of a very unstable N,N ‐dimethyl‐(1,3‐dimethyl‐4‐aminouracil‐5‐yl)azidomethyleniminium chloride (amide azide) ( 8 ) which would undergo an in situ rearrangement into very likely, a 4‐amino‐5‐(chloroformamidin‐1′‐yl)uracil and/or related compounds of types 10 . Depending on reaction conditions, the latter was proved to be a very good precursor of the 8‐dimethylaminotheophylline 11 as well.