To solution of 5-allyloxyindole-2-carboxylic acid ethyl ester (1.0 g, 4.08 mmol) in THF (10 mL) was added azodicarboxylic acid bis[dimethylamide] (TMAD; 1.4 g, 8.15 mmol). After stirring at room temperature for 20 min, 2-(3-thienyl)ethanol (0.78 g, 6.12 mmol) was added followed by the addition of tributyl phosphine (1.65 g, 8.15 mmol). After stirring at room temperature for 18 h, the reaction was partitioned between ethyl acetate and water. The organic layer was washed with brine and dried over Na2SO4. Purification by flash colunmn chromatography (silica gel, EtOAc/hexanes) yielded the desired product as an oil (1.36 g, 94%).
