In a 100 mL round bottom flask, 5-cyanoindole (2.0 g, 14.07 mmol) was dissolved in 20 mL of anhydrous tetrahydrofuran (THF). To this solution, 4-dimethylaminopyridine (DMAP, 0.86 g, 7.03 mmol) was added and the mixture was stirred for 0.5 h at room temperature. Subsequently, di-tert-butyl dicarbonate (Boc2O, 3.07 g, 14.07 mmol) was added and the reaction continued to be stirred for 2 hours. After completion of the reaction, the reaction was quenched with water and extracted with ether (2×). The organic layers were combined, washed sequentially with 1N hydrochloric acid, water and saturated brine, dried over anhydrous magnesium sulfate (MgSO4) and concentrated to give 1-Boc-5-cyanoindole (3.26 g, 96% yield) as a white solid. The product was characterized by 1H NMR (DMSO-d6): δ 8.20-8.14 (m, 2H), 7.83 (d, 1H), 7.70 (d, 1H), 6.80 (d, 1H), 1.63 (s, 9H).
