The synthesis of β-nitropyridine compounds

Pyridine and a number of substituted pyridines have been nitrated by reaction with N2O5 followed by reaction with an aqueous solution of SO(2)xH(2)O or NaHSO3. The dependence of the yields on the pH of the aqueous reaction medium, on the concentration of SO(2)xH(2)O-HSO3-, on addition of methanal to the aqueous phase, and on the reaction temperature were investigated. The yields obtained with NaHSO3 were: 3-nitropyridine 77%, 2-methyl-5-nitropyridine 36%, 3-methyl-5-nitropyridine 24%, 3-acetyl-5-nitropyridine 18%, 5-nitropyridine-3-carboxylic acid 15%, 3-chloro-5-nitropyridine 11%, 4-methyl-3-nitropyridine 39%, 4-acetyl-3-nitropyridine 67%, 4-cyano-3-nitropyridine 45%, 4-phenyl-3-nitropyridine 68%, 4-formyl-3-nitropyridine 62% (from reaction in liquid SO2), 3-nitropyridine-4-carboxylic acid 48%, methyl 3-nitropyridine-4-carboxylate 75%, 2,3-dimethyl-5-nitropyridine 37%, 2,4-dimethyl-5-nitropyridine 64%, 3-nitroquinoline 10% and 4-nitroisoquinoline 42%.