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 p resence of NH3 afforded 4,5-disubstituted pyrimidines 5. Use of ammonium ac etate instead of NH3 as the nitrogen source caused another ring transformat ion giving 5,6-disubstituted 3-nitro-2-pyridones 8 as well as 5. Pyrimidino ne 1 behaved as an activated diformylamine 6 in the former reaction and as the synthetic equivalent of alpha-nitroformylacetic acid 9 in the latter ca se. The ratio of 5 and 8 produced when using NH4OAc varied with solvent. Th e reaction in acetic acid predominantly afforded pyrimidine 5, but in metha nol the reaction afforded pyridone 8. The two types of ring transformations presented here are novel methods for the preparation of azaheterocycles.