A new route to the synthesis of 4-amino-substituted pyrido[2,3-d]pyrimidin-5-one derivatives

The reaction of 6-(R-amino)-5-acetyl-4-methylsulfonyl-2-phenylpyrimidines with amines was studied. 6-Arylamino derivatives react with alkylamines to form 6-alkylamino-4-arylamino-5-acetyl-2-phenylpyrimidines, which upon refluxing in benzene with dimethylformamide dimethylacetal are converted to 4-alkylamino-8-aryl-2-phenylpyrido[2,3-d]pyrimidin-5(8H)-ones. The cyclization proceeds selectively with participation of the arylamino group only, the alkylamino group being not involved. At the same time, refluxing of 5-acetyl-4,6-dibenzylamino-2-phenylpyrimidine with dimethylformamide dimethylacetal in toluene affords the product of condensation on the acetyl group, which upon refluxing in o-xylene transforms to 4-benzylamino-8-benzyl-2-phenylpyrido[2,3-d]pyrimidin-5(8H)-one.