On the Amination of Halogenonitropyridines

Article abstract of DOI:10.1021/jo00204a012

Evidence is presented, based on 15N-labeling experiments and 1H NMR spectroscopy, that the conversion of 2-chloro-5-nitropyridine (1) into 2-amino-5-nitropyridine by treatment with potassium amide/liquid ammonia proceeds to about 75percent according to a sequence of reactions involving addition of the amide ion to C-6, ring-opening, and ring-closure N(ANRORC) mechanism>.On the contrary, 2-chloro-3,5-dinitropyridine (11) is nearly quantitatively aminated by liquid ammonia (containing no potassium amide) into 2-amino-3,5-dinitropyridine according to an S_N(AE) process, thus no ring-opening being involved.As shown by NMR spectroscopy, the position of addition of liquid ammonia to 11 is temperature dependent.At -60 deg C the addition takes place at C-4, while at -40 deg C the addition at C-6 is strongly favored.Apparently the addition at C-4 is kinetically controlled; the addition at C-6 leads to the thermodynamically more stable adduct.Amination of 11 with liquid ammonia in the presence of potassium permanganate yields mainly 2,6-diamino-3,5-dinitropyridine.