Synthesis of pyrido [2,3-d] pyrimidines from 2-amino-3cyanopyridines

The preparation of a number of 1-arylpyrido [2,3-d] pyrimidine-2,4-[lH,3H]-diones is described. Treatment of 2-chloro-3-cyanopyridine with primary aromatic amines afforded the corresponding 2-arylamino derivatives which were hydrolyzed with 40 percent H2SO4 to 2-arylamino-3-pyridinecarboxylic acids. The reaction of the latter compounds with urea yielded the desired pyrido [2, 3-d] pyrimidines. 2-anilino-3-cyanopyridine [II] was allowed to react with urea at 250 degree to give 4-imino-l-phenylpyrido [2, 3-d] pyrimidin-2-[1H, 3H]-one as shown by ir, nmr and mass spectra. Reacting II with ethyl chloroformate yielded the corresponding N-ethoxycarbonyl derivative which upon reaction with hydrazine, it was deacetylated and reverted back to II