Methyl triphenylphosphonium bromide (2.2 g, 6.17 mmol) was suspended in anhydrous tetrahydrofuran (20 mL) and stirred under nitrogen on an ice bath. 2.5M n-Butyllithium in hexanes (2.3 mL, 5.75 mmol) was added at such a rate that temperature did not exceed 3° C. Stirring was continued at room temperature for 1 hr. The reaction mixture was cooled on an ice bath and a solution of 4 (1.3 g, 3.08 mmol) in tetrahydrofuran (8 mL) was added at such a rate that temperature did not exceed 3° C. Stirring was continued at room temperature overnight. The reaction mixture was poured on saturated ammonium chloride (150 mL) and extracted with ethyl acetate (150 mL). The organic extract was washed with water (2×80 mL) and dried over sodium sulfate. The solvent was removed on a rotary evaporator and the crude product was purified by chromatography on silica (80 g) with 2% ethyl acetate in heptane (2 L), then 4% (4 L) to produce 5 (1.18 g, 91%).
