A mixture of 5-hydroxy-1H-indole-2-carboxylic acid ethyl ester (2 g, 10 mmol), 2-bromo-1-pyrrolidin-1-yl-ethanone (3 g, 20 mmol) and cesium carbonate (19.5 g, 60 mmol) in dimethylformamide (16 mL) was stirred at room temperature for 24 hours. The reaction was diluted with ethyl acetate (150 mL), washed with water (5×50 mL) and brine, dried and concentrated. The residue was recrystallized from ethyl acetate and hexane to give 0.8 g (25%) 5-(2-oxo-2-pyrrolidin-1-yl-ethoxy)-1H-indole-2-carboxylic acid ethyl ester as a brown solid.
