Two-step synthesis of (Z) -2 -[2 -oxo -2,3 -dihydropyrido [2,3 -d]pyrimidin -4 (1H)-ylidene]acetamide derivatives from 2-chloro-6-methylpyridine-3-carbonitrile

(Z)-2-[1-Aryl-7-methyl-2-oxo-2,3-dihydropyrido[2,3-d]pyrimidin-4(1H)-ylidene]acetamides were prepared using a two-step sequence. The first step was the addition of magnesium enolates of tertiary acetamides to 2-chloro-6-methylpyridine-3-carbonitrile to give vinylogous urea derivatives, (Z)-3-amino-3-(2-chloro-6-methylpyridin-3-yl)propenamides. In the second step, these were reacted with aryl isocyanates in the presence of sodium hydride to give the corresponding pyrido[2,3-d]pyrimidin-2(1H)-one derivatives.