Amination of 3,6‐dinitro‐1,8‐naphthyridines

Treatment of 2‐amino‐3,6‐dinitro‐1,8‐naphthyridines with liquid ammonia/potassium permanganate gives 2,4‐diamino‐3,6‐dinitro‐1,8‐naphthyridine. From 2‐ethoxy‐3,6‐dinitro‐1,8‐naphthyridine a mixture of 4‐amino‐and 5‐amino‐3,6‐dinitro‐1,8‐naphthyridine was obtained. 2‐Chloro‐3,6‐dinitro‐1,8‐naphthyridine afforded a mixture of four compounds i. e. 2,4‐ and 2,5‐diamino‐3,6‐dinitro‐1,8‐naphthyridine and 2‐chloro‐5‐amino‐3,6‐dinitro‐1,8‐naphthyridine and 2‐amino‐3,6‐dinitro‐1,8‐naphthyridine. A study on covalent amination has shown that 4‐amino‐2‐ethoxy‐3,6‐dinitro‐1,8‐naphthyridine undergoes covalent amination at C‐5, whereupon in this adduct amino‐deethoxylation takes place. In a similar way, 2‐chloro‐ and 2‐ethoxy‐5‐amino‐3,6‐dinitro‐1,8‐naphthyridine give covalent amination at C‐4.