Acetic Anhydride → 1-(5-Methyl-6-nitro-1H-indazol-1-yl)ethanone

Participants

Reaction Steps

Five g (28,2 m-mol) of 5-methyl-6-nitro-1H-indazole (formula 24) prepared e.g. according to the method described by E. Nolting, Ber. Dtsch. Chem. Ges. 37 (1904) 2556 were added to a mixture of acetic acid (50 ml) and acetic anhydride (100 ml). After about 15 min the acetylated compound (formula 25) crystallized from the light-yellow colored solution in the form of elongated colorless needles. To complete crystallization, the solution was left to stand for a period of 45 min at room temperature and for a period of 15 hours in a refrigerator (4°). The crystal mass formed was filtered under suction, washed well with water and dried over P2O5 under vacuum. This yielded 4.6 g (yield 75%) of the formula 25 target product. By careful evaporation of the mother liquor and allowing to stand overnight in the refrigerator, an additional portion (0.90 g) of the target product was obtained. Total yield was 5.55 g (90%). The target product melts at 185°; ir (KBr): 1715 (ester carbonyl), 1582 (aromatic), 1530 cm-1 (NO2); pmr (CDCl3): δ 2.66 (s, 3, C5 --CH3), 2.82 (s, 3, N1 --CH3CO), 7.70 (s, 1, H4), 8.18 (s, 1, H7), 8.96 (s, 1, H3); ms (70 eV): m/e 219 (35%, M+), 177 (61%, M+ -keten), 160 (100%, M+ -keten-HO).

Provenance & Evidence