To a suspension of 6-chloro-5-(5,5-dimethyl-1,3,2-dioxaborinan-2-yl)-1H-indole (150 mg, 0.57 mmol) in mixture solvent of 1,4-dioxane/N,N-dimethylformamide (5:1, 3 mL) was added vilsmeier salt (165 mg, 1.71 mmol) under nitrogen. The mixture was stirred at room temperature for 30 minutes under nitrogen. Potassium carbonate (2.0M in water, 1.5 mL) was added and stirred for 10 minutes, followed by the addition of tert-butyl 2-(4-bromophenyl)pyrrolidine-1-carboxylate (180 mg, 0.55 mmol), the mixture was degassed with nitrogen for 10 min., then treated with Pd(dppf)Cl2 (62 mg, 0.086 mmol). The reaction mixture was stirred at 90° C. for 30 minutes. The mixture was filtered through a Celite pad and the filtrate was partitioned between ethyl acetate (10 mL) and water (20 mL). The aqueous phase was extracted two times with ethyl acetate (10 mL), the combined organic layers were washed with brine (15 mL), dried over sodium sulfate, filtrated, and concentrated to afford crude product which was purified by silica-gel chromatography to give the title compound (170 mg, 72.2% yield).
