Two Ring Transformations of 3-Methyl-5-nitropyrimidin-4(3H)-one for the Construction of Azaheterocycles.

The reaction of 3-methyl-5-nitropyrimidin-4(3H)-one 1 with ketones in the presence of NH3 afforded 4,5-disubstituted pyrimidines 5. Use of ammonium acetate instead of NH3 as the nitrogen source caused another ring transformation giving 5,6-disubstituted 3-nitro-2-pyridones 8 as well as 5. Pyrimidinone 1 behaved as an activated diformylamine 6 in the former reaction and as the synthetic equivalent of α-nitroformylacetic acid 9 in the latter case. The ratio of 5 and 8 produced when using NH4OAc varied with solvent. The reaction in acetic acid predominantly afforded pyrimidine 5, but in methanol the reaction afforded pyridone 8. The two types of ring transformations presented here are novel methods for the preparation of azaheterocycles.