Synthetic applications of N–N linked heterocycles. Part 9. Preparation of α-(4-pyridyl)nitroalkanes and N-(4-pyridyl)azoles by regiospecific attack of nitroalkyl and azolyl anions on N-(2,6-dimethyl-4-oxopyridin-1-yl)pyridinium salts
Sodium salts of nitroalkanes and of azoles react with N-(2,6-dimethyl-4-oxopyridin-1-yl)pyridinium salts (1)–(3) to give regiospecifically 1,4-dihydropyridines (12)–(14), (15), and (16) in high yields. Photolysis of the dihydropyridines gives α-(4-pyridyl)nitroalkanes (7)–(9) and N-(4-pyridyl)azoles in moderate to good yields. Certain azolyl dihydropyridines revert to the parent azole on photolysis; this appears to be a steric effect.