Substituent effects on the isomer ratios in the rearrangement of some 2- and 4-nitraminopyridines

The preparation, and rearrangement in 92% sulfuric acid, of 4-X-2-nitramino- (1), 2-X-4-nitramino-(2), and 6-X-2-nitramino-pyridines (3) is reported (X = H, Me, MeO, Br, Cl, CO2H). The product isomer ratios can be explained by differential electronic stabilization of the appropriate a complexes for aromatic nitration and steric effects seem relatively unimportant. Deuteration [3-D in series (1), X = Me] had no effect on the product distribution.