SYNTHESIS OF FUNCTIONALIZED PYRIMIDINE-4-THIONES AND DERIVATIVES OF PYRIDO[2,3-D]PYRIMIDINE-5-ONE FROM MONOACYLKETENE ANIMALS

Monoacylketene animals containing an unsubstituted NH2 group react as C-nucleophiles with benzoyl isothiocyanate to give the corresponding t hioamides which undergo cyclization by sodium methoxide in methanol to afford R-amino-5-acetyl-2-phenyl-3H-pryimidine-4-thiones. A scheme fo r constructing the pyrido[2,3-d]pyrimidine system from keteneaminals i s offered. The reaction of -R-amino-5-acetyl-2-phenyl-3H-pyrimidine-4- thiones with dimethylformamide dimethylacetal leads to N-4-methylthio- 8H-pyrido-[2,3-d]pyrimidine-5-ones. Cyclization of tyl-6-benzoylamino- 4-methylthio-2-phenylpyrimidine by sodium methoxide yields N-unsubstit uted 4-methylthio-8H-pyrido[2,3-d]pyrimidine-5-one.