Oxonium, trimethyl-, tetrafluoroborate(1-) (1:1) → 2,3-Dimethyl-6-nitro-2H-indazole

Participants

Reaction Steps

To a stirred solution of 18.5 g (0.11 mol) of 3-methyl-6-nitro-1H-indazole in 350 ml acetone, at room temperature, was added 20 g (0.14 mol) of trimethyloxonium tetrafluoroborate. After the solution was allowed to stir under argon for 3 hours, the solvent was removed under reduced pressure. To the resulting solid was added saturated aqueous NaHCO3 (600 ml) and a 4:1 mixture of chloroform-isopropanol (200 ml), and the mixture was agitated and the layers were separated. The aqueous phase was washed with additional chloroform: isopropanol (4×200 ml) and the combined organic phase was dried (Na2SO4). Filtration and removal of solvent gave a tan solid. The solid was washed with ether (200 ml) to afford 2,3-dimethyl-6-nitro-2H-indazole as a yellow solid (15.85 g, 73%). 1H NMR (300 MHz, d6DMSO) δ 8.51 (s, 1H), 7.94 (d, J=9.1 Hz, 1H), 7.73 (d, J=8.9 Hz, 1H), 4.14 (s, 3H), 2.67 (s, 3H). MS (ES+, m/z) 192 (M+H).

Provenance & Evidence