Synthesis of 5‐mono‐ and 5,7‐diamino‐pyrido[2,3‐ d ]‐pyrimidinediones with potential biological activity by regioselective amination

5‐Alkyl‐/arylamino‐ and 5,7‐dialkyl/arylamino‐pyrido[2,3‐ d ]pyrimidine‐2,4‐diones ( 4,5, 7‐9 ) were prepared from the corresponding 5,7‐dichloro‐pyrido[2,3‐ d ]pyrimidine‐2,4‐diones 2 with aliphatic and aromatic amines 3 and 6 in a regioselective reaction. The 7‐monoazides 10 , obtained by azidation of 5‐amino‐7‐chloro derivatives 4 , were converted to iminophosphoranes by reaction with triphenyl‐phosphane via Staudinger reaction. Hydrolysis with aqueous acetic acid produced in one step 7‐unsubstituted‐amino‐pyrido[2,3‐ d ]pyrimidine‐2,4‐diones 12 . In a similar amination reaction, 5‐chloropyrido[2,3‐ d ]pyrimidine‐2,4,7‐triones 13 were aminated and formylated to 5‐alkyl/arylamino‐6‐formyl derivatives 14 ‐ 16 in a combined one‐step‐reaction with bulky arylamines or alkylamines in the presence of dimethylformamide.