To a solution of 5-hydroxyindole (2.0 g, 0.015 mol) in acetonitrile (20 mL) was added anhydrous potassium carbonate (4 g, 0.028 mol) with vigorous stirring followed by 2-iodopropane (3 g, 0.018 mol). The reaction mixture was stirred at room temperature for 2 days, filtered and the solid was washed with acetonitrile. The filtrate was concentrated and purified by fast chromatography (80% hexane/20% ethyl acetate) to afford 5-isopropoxy-1H-indole (1.72 g, 83% yield) as a light yellow oil (M + 1 = 176.1).
[1] Patent: WO2005/9958, 2005, A1. Location in patent: Page 102
[2] Patent: US2005/288354, 2005, A1
[3] Journal of Medicinal Chemistry, 2007, vol. 50, # 12, p. 2865 - 2874