Abstract
Reaction of diketene with 2-aminopyridine (Ia), 2-amino-4-methylpyridine (Ib), and 2-amino-3-methylpyridine (Ic) gave 2-methyl-4H-pyrido [1, 2-a] pyrimidin-4-one (Ma), 2, 8-dim.ethyl-4H-pyrido [1, 2-a] pyrimidin-4-one (IIIb), and 2, 9-dimethyl-4H-pyrido [1, 2-a]-pyrimidin-4-one (IIIc), respectively. Isomeric 2-one derivatives, such as 4-methyl-2H-pyrido [1, 2-a] pyrimidin-2-one (IVa) and 4, 8-dimethyl-2H-pyrido [1, 2-a] pyrimidin-2-me (IVb), were prepared by reaction of α-bromccrotonic acid with Ia and Ib, respectively. The differences were sufficiently great to permit mass, nuclear magnetic resonance, infrared and ultraviolet spectral data in a distinction of the structures between the 4-one (III) and 2-one derivatives (IV).
