Treatment of either a pyrido [4, 3-d][1, 3] oxazin-4-one or an ethyl 4-amidonicotinate with amines yields a 4-amidonicotinamide which may be cyclised by longer contact with the amine, or by heat, to give a pyrido [4, 3-d]-pyrimidin-4 (3H)-one. Some typical infrared and nuclear magnetic resonance spectra are discussed.