Amination of 4-nitropyridazine 1-oxides by liquid ammonia/potassium permanganate

Treatment of 4-nitropyridazine 1-oxide (1a) 3-methoxy-6-chloro-4-nitropyridazine 1-oxide (1b) or 3,6-dimethoxy-4-nitropyridazine 1-oxide (1c) with a solution of potassium permanganate in liquid ammonia gives in reasonable-to-good yields the corresponding 5-amino-4-nitropyridazine 1-oxides (75%, 54% and 62%, respectively). 3,6-Dimethoxypyridazine (4a) and 3-methoxypyridazine (4b) are converted into the corresponding 4-aminopyridazines 6a,6b on treatment with potassium amide/liquid ammonia/potassium permanganate (yield 50 and 22% respectively). In the last-mentioned reaction besides 6b 3,3′-dimethoxy 4,4′-bipyridazine (7, 23%) was obtained. It is suggested that the neutral 1:1 σ-adducts formed between (1a–1c) and liquid ammonia and the anionic σ-adducts, formed between (5a–5b) and potassium amide are intermediates in this amino-oxidation reaction.