1-Benzenesulfonyl-5-bromoindole. A mixture of 5-bromoindole (5 g, 25.5 mmol) and tetra-n-butylammonium hydrogen sulfate (866 mg, 2.55 mmol) in 50% NaOH (50 mL) and toluene (200 mL) is stirred at room temperature for 5 min. Benzenesulfonyl chloride (3.57 mL, 28 mmol) is added and the mixture stirred for 1 hr. The mixture is diluted with water (500 mL) and extracted with EtOAc (3×100 mL). The extracts are washed with brine (250 mL), dried over MgSO4, filtered and evaporated to a yellow oil. The oil is purified by medium-pressure column chromatography on silica gel eluting with 10% EtOAc/hexanes to give the title compound as a white solid (7.81 g).
