Scope of reactions for (R, Z)-3^a.

^aUnder Ar atmosphere, a mixture of 1 (0.20 mmol), 2 (0.40 mmol), C1 (8 mol%) and B2 (8 mol%) in CH₂Cl₂ (8.0 mL) was stirred at room temperature (rt) for 5 min, then it was cooled to 0 °C for 6 h. Products (R, Z)-3 were obtained in isolated yields. The ee was determined by chiral-HPLC analysis.