Covalent amination of 3,6‐dinitro‐1,8‐naphthyridines

The preparation of 3,6‐dinitro‐2‐R‐1,8‐naphthyridines ( 1 , R = OH, NH 2 , OC 2 H 5 , Cl) is described and their addition patterns with liquid ammonia are studied. Compound 1 (R = OH, NH 2 ) gives with liquid ammonia at ‐ 45° as well as at room temperature formation of the covalent ó‐adduct 4‐amino‐1,4‐dihydro‐3,6‐dinitro‐2‐R‐1,8‐naphthyridine ( 2 , R = OH, NH 2 ). Compound 1 (R = OC 2 H 5 ) yields with ammonia at ‐ 45° two σ‐adducts, i.e. the C‐4 adduct ( 2 , R = OC 2 H 5 ) and the C‐5 adduct 5‐amino‐5,8‐dihydro‐3,6‐dinitro‐2‐R‐1,8‐naphthyridine ( 3 , R = OC 2 H 5 ). The ratio is about 50:50. This ratio depends on the temperature; at room temperature the C‐5 adduct is more favoured. After staying overnight the ethoxy group has been exchanged for the amino group, yielding 2 (R = NH 2 ). With 1 (R = Cl) both adducts 2 (R = CI) and 3 (R = CI) were formed, the C‐4 adduct 2 (R = CI) is more favoured at room temperature. Prolonged treatment with liquid ammonia leads to an exchange of the chloro atom by the amino group, yielding 2 (R = NH 2 ).