To a solution of 3-benzyl-4-(1H-indol-5-yl)-piperazine-1-carboxylic acid tert-butyl ester (0.17 g, 0.4 mmol) in 2.5 mL DMF was added powdered KOH (0.060 g, 1.1 mmol), followed by I2 (0.11 g, 0.4 mmol) in DMF. The solution was stirred for 45 minutes and then treated with 10% aqueous Na2S2O3. The mixture was extracted with EtOAc, and the combined organic layers were dried over MgSO4, filtered, and concentrated under reduced pressure. The residue was immediately taken up in 2 mL DMF and treated with 60% NaH (0.02 g, 0.5 mmol). After 20 minutes the solution was treated with benzenesulfonyl chloride (0.07 mL, 0.5 mmol). After 30 minutes of stirring the mixture was quenched with H2O and extracted with EtOAc. The combined organic layers were washed with H2O, washed with brine, dried over MgSO4, filtered, and concentrated under reduced pressure. Purification via flash chromatography (30% EtOAc in hexanes) afforded 4-(1-benzenesulfonyl-3-iodo-1H-indol-5-yl)-3-benzyl-piperazine-1-carboxylic acid tert-butyl ester (0.23 g, 83%) as a white foam; MS (M+H)=658.
