Reaction of diketene with ethyl pyridineformimidates (Ia-e) resulted in the formation of 6-methyl-2-pyridyl-4H-1, 3-oxazin-4-one (IVa-c) and 2-ethoxy-6-methyl-2-pyridyl-2H-1, 3-oxazin-4 (3H)-one (IIIb, c). Similar reaction with ethyl 2-quinolineformimidate (Id) and methyl 2-pyridineacetimidate (Ie) gave 6-methyl-2-(2-quinolyl)-4H-1, 3-oxazine-4-one (IVd) and 2-methoxy-6-methyl-2-(2-pyridylmethyl)-2H-1, 3-oxazin-4 (3H)-one (IIIe), respectively. The products obtained were treated with ammonia to give 6-methyl-2-substituted-4 (3H)-pyrimidone (Va-e). Hydrolysis of IIIe gave 6-hydroxy-4-methyl-3 (or 5)-(2-pyridyl)-2 (1H)-pyridone (VIII).