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Oxidation of 5-hydroxyaminopyridine-2-sulfonic acid (1) to 5-nitropyridine-2-sulfonic acid (2) may be performed selectively by SPB in acetic acid, bleach in water or potassium permanganate in water, with the last as the preferred one. The structure of 2 was verified by X-ray crystallography. The crude products proved difficult to purify efficiently due to inorganic impurities, but substitution of the sulfonyl group in 2 with methanol yielded 2-methoxy-5nitropyridine (6) in 44, 42 and 57 % overall yield from 1, respectively from the three methods. The reaction of 1 with SPC afforded 5,5’-azoxypyridine-2,2’-disulfonic acid (3) which, upon treatment with methanol gave 5,5’-azoxypyridine-2,2’-dimethoxypyridine (5) in 57 % yield from 1.

5-Nitropyridine-2-sulfonic acid, a new precursor for 2,5-disubstituted pyridines