p-Toluenesulfonic acid → 5-bromo-7-fluoro-1-(tetrahydro-2H-pyran-2-yl)-1H-indazole

Participants

Reaction Steps

To a mixture of 5-bromo-7-fluoro-1H-indazole (9.3 g, 43.26 mmol) and DHP (4.36 g, 51.9 mmol) in dry dichloromethane (100 mL), was added PTSA (424 mg, 2.16 mmol) at room temperature. The resulting mixture was stirred overnight. Work-up: saturated aqueous NaHCO3 (30 mL) was slowly added to the reaction mixture. The organic layer was separated, dried over Na2SO4, and concentrated in vacuo. The residue was purified by column chromatography on silica gel (0-10% EtOAc in petroleum ether) to give 5-bromo-7-fluoro-1-(tetrahydro-2H-pyran-2-yl)-1H-indazole as a light yellow solid. (7.8 g). 1H NMR (300 MHz, CDCl3): δ 7.98 (s, 1H), 7.64 (s, 1H), 7.22 (dd, 1H), 5.84 (dd, 1H), 4.07-4.02 (m, 1H), 3.78-3.71 (m, 1H), 2.62-2.53 (m, 1H), 2.16-2.07 (m, 2H), 1.79-1.71 (m, 2H), 1.63-1.33 (m, 1H).

Provenance & Evidence