4-Trifluoromethanesulfonyloxy-7-[1-(tert-butoxycarbonyl)-5-(piperidinomethyl)indol-2-yl]isoindolinone (300 mg, 0.505 mmol) was dissolved in acetonitrile (15 mL), and the solution was added with zinc cyanide (178 mg, 1.52 mmol) and [bis(diphenylphosphino)ferrocene]dichloropalladium (33 mg, 0.0404 mmol), followed by stirring at 90° C. for 17 hours under argon atmosphere. The reaction mixture was added with water and extracted with ethyl acetate. The organic layer was washed with saturated brine and dried over sodium sulfate. The solvent was evaporated under reduced pressure. The residue was purified by preparative thin-layer chromatography (chloroform/methanol=8/1) to obtain 4-cyano-7-[1-(tert-butoxycarbonyl)-5-(piperidinomethyl)indol-2-yl]isoindolinone (198 mg, yield 83%).
