Abstract
Ethyl N-(2-pyridyl) formimidate (Va) reacted with diketene to give 3-acetyl-4H-pyrido [1, 2-a] pyrimidin-4-one (VIIa) and ethyl 2-(2-pyridylaminomethylene) acetoacetate (VIIIa). Reaction of diketene with ethyl N-(2-pyridyl) acetimidate (Vb) and ethyl N-(2-pyridyl) propionimidate (Vc) afforded 4H-pyrido [1, 2-a] pyrimidine derivatives (VIIb and VIIc), respectively. Similarly 2-benzylideneaminopyridine (VIa) reacted with diketene to give 3-acetyl-4-hydroxy-2-phenyl-4H-pyrido-[1, 2-a] pyrimidine (XI). On the other hand, reaction of trimethylsilyl isocyanate with Va, Vb, and Vc gave rise to 4H-pyrido [1, 2-a]-sym-triazin-4-one derivatives (XIXa, XIXb, and XIXc), respectively. Reaction of phenyl isocyanate with VIa afforded 2, 3-diphenyl-4H-pyrido [1, 2-a]-sym-2, 3-dihydrotrazin-4-one (XX).
