To a stirring mixture of 4 (3.58 g, 8.72 mmol) and Et3N (6.1 ml, 43.6 mmol) was added Me3SiOSO2 CF3 (2.56 mL, 13.0 mmol) at 0° C. under positive pressure of dry Ar. The mixture was stirred for 30 min at the same temperature, and then partitioned between CH2Cl2 and sat. aqueous NaHCO3. The organic layer was dried (Na2SO4) and evaporated. The residue was dissolved in DMSO (12 mL). To this solution was added Pd(OAc)2 (98 mg, 0.44 mmol), and the mixture was stirred for 36 h under positive pressure of O2. The mixture was partitioned between EtOAc and brine. The organic layer was dried (Na2SO4), evaporated, and chromatographed on a silica gel column (hexane/EtOAc=5/1) to give 5 (3.13 g, 88%) as a white solid.
