A CONVENIENT SYNTHESIS OF 1,3-DISUBSTITUTED 4-THIOXO-3,4-DIHYDROPYRIDO[2,3-d]PYRIMIDIN-2(1H)-ONES AND 4-THIOXO-3,4-DIHYDROPYRIDO[4,3-d]PYRIMIDIN-2(1H)-ONES

摘要

The reaction of 2-chloro-3-lithiopyridine with alkyl isothiocyanates gave the corresponding N-alkyl-2-chloropyridine-3-thiocarboxamides, which in turn were allowed to react with aryl isocyanates in the presence of sodium hydride as a base to give 3-alkyl-1-aryl-4-thioxo-3,4-dihydropyrido[2,3-d]pyrimidin-2(1H)-ones. A similar sequence starting from 4-chloro-3-lithiopyridine and ethyl isothiocyanate gave 1-aryl-3-ethy1-4-thioxo-3,4-dihydropyrido[4,3-d]pyrimidin-2(1H)-ones, via 4-chloro-N-ethylpyridine-3-thiocarboxamide.