On the reaction of 3,4-dihydropyrimidones with nitric acid. Preparation and X-ray structure analysis of a stable nitrolic acid

A series of substituted 3,4-dihydro-2-pyrimidones (DHPMs) was reacted with nitric acid under different reaction conditions. Treatment of DHPMs with 50-65% nitric acid at 0 degreesC led to the formation of the corresponding dehydrogenated 2-pyrimidones in moderate to good yields. In contrast, reaction of one representative DHPM with 60% nitric acid at 50 degreesC led to an unusually stable nitrolic acid, involving a formal nitration, nitrosation, and dehydrogenation step. The molecular structure of this product was determined by X-ray crystallographic analysis.