4-Bromo-2-methylaniline → 5-bromo-1H-indazole

Participants

Reaction Steps

4-bromo-2-methylaniline (5.0 g, 27 mmol) was added to a mixture of water (12.3 ml) and HBF4 (48% by weight in water, 12.3 ml, 67 mmol) in a Nalger reaction vessel cooled in an ice water bath. Then, NaNO2 (1.85 g, 27 mmol) in water (3.8 ml) was added while maintaining the temperature of the reaction around 10 C. After 15 minutes, the was then recooled in an ice water bath and filtered via a Buchner funnel. The solid was washed with cold 5% aqueous HBF4, cold MeOH (20 ml) and diethyl ether (3×10 ml). The solid was dried on a Buchner funnel for 1 hour and then added to a flask containing KOAc (5.3 g, 54 mmol, dried in vacuo overnight) and 18-c-6 (0.35 g, 1.3 mmol) suspended in chloroform (250 ml). The reaction was stirred at room temperature for 2 hours and then filtered, and the solid was washed with chloroform. The filtrate was washed with water and brine, dried over sodium sulfate, filtered, concentrated, and diluted with water (250 ml). The suspension was filtered, and the solid was washed with hexanes (50 ml) and diethyl ether (50 ml), collected, and dried in vacuo to give title compound (3.6 g, 68%). MS (ESI pos. ion) m/z: 197 (M+H). Calc'd Exact Mass for C7H5BrN2: 196.

Provenance & Evidence