Two ring transformations of 3-methyl-5-nitropyrimidin-4(3H)-one for the construction of azaheterocycles

Abstract

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.