(R)-(+)-α,α-Diphenyl-2-pyrrolidinemethanol Trimethylsilyl Ether

Experimental procedure³⁾: Chloroacetic acid (21.8 mg, 0.231 mmol) is added to a solution of 1 (225 mg, 1.73 mmol), 2 (200 mg, 1.16 mmol) and 3 (18.8 mg, 0.058 mmol) in CH₂Cl₂ (2 mL) at 23 °C under Ar atmosphere. The reaction mixture is stirred for 40 min at 23 °C followed by addition of 4 (409.2 mg, 1.73 mmol) and Cs₂CO₃ (1.13 g, 3.47 mmol) at 0 °C. After the resulting suspension is stirred for additional 3 h at 0 °C, the solvent is removed under reduced pressure at 0 °C. EtOH (3 mL) is added to the crude mixture. The resulting mixture is stirred for 15 min at 23 °C before addition of p-toluenethiol (716.7 mg, 5.78 mmol) at –15 °C. The resulting mixture is stirred for 36 h at same temperature before being quenched with cold 2 mol/L HCl. The aqueous layer is extracted three times with CHCl₃. The combined organic layer is washed with saturated aqueous NaHCO₃, dried over MgSO₄, and concentrated under reduced pressure. Flash chromatography (SiO₂, EtOAc:hexane = 5:95 – 10:90) provides 5 (413.7 mg, 70%) as colorless oil.