NUCLEOPHILIC ADDITIONS TO N-NITROPHENYL)-PYRIDINIUM AND N-(2,4-DINITROPHENYL)-PYRIDINIUM SALTS

The reactive N-nitropyridinium nitrate (2) and the stable N-(2,4-dinit rophenyl)-pyridinium chloride (5) have been reacted with nucleophiles. N-Nitrupyridinium nitrate and pyridine gave 4-pyridino-1-nitro-1,4-di hydropyridine (3) in an equilibrium reaction. With hydroxide ions. a r ing-opening reaction took place to give 5-nitroaminopenta-2,4-dienal ( 4) which gave back 2 upon acidification, N-(2,4-Dinitrophenyl) pyridin ium chloride reacted with sodium sulfite to give a mixture of two prod ucts. one from attack of two sulfite ions on the dinitrophenyl ring (7 ) and one from attack in the 4-position of the pyridinium ring (6). Th e ratio 7:6 increased with increasing polarity of the reaction medium. N-(2,4-Dinitrophenyl)pyridinium chloride also reacted with nitrometha nide ion to give 4-dinitrophenyl)-4-nitromethyl-1,4-dihydropyridine (9 ). This compound reacted with NO2BF4 to give the N-(2,4-dinitrophenyl) -4-nitromethylpyridinium ion (10).