To a mixture of NaH (60% suspension in mineral oil, 0.24 g, 6.12 mmol) and DMF (20 mL) was added 5-allyloxyindole-2-carboxylic acid ethyl ester (1.0 g, 4.08 mmol), from Example 1(d). After stirring at room temperature for 1 h, 6-chloropiperonyl chloride (0.84 g, 4.08 mmol) was added followed by the addition of tetrabutyl ammonium iodide (0.15 g, 0.41 mmol). The reaction was stirred at room temperature for 18 h. When the reaction was complete as indicated by TLC, the reaction mixture was partitioned between EtOAc and water. The organic layer was washed with brine and dried (Na2SO4). The solvent was removed in vacuo and the resulting crude product was purified by flash column chromatography (silica gel, EtOAc/hexanes) to yield the desired product as an oil (0.72 g, 43%). LC/MS (ES+) m/e 414.0 [M+H]+.
