Ring transformations of heterocycles with nucleophiles. 33. Cycloadditions of 5-nitropyrimidines with ynamines. Formation of 3-nitropyridines, N-5-pyrimidyl-.alpha.-carbamoylnitrones, and 2,2a-dihydroazeto[2,3-d]-3,5-diazocines
Ring transformations of heterocycles with nucleophiles. 33. Cycloadditions of 5-nitropyrimidines with ynamines. Formation of 3-nitropyridines, N-5-pyrimidyl-.alpha.-carbamoylnitrones, and 2,2a-dihydroazeto[2,3-d]-3,5-diazocines