General procedure for the Pd-catalyzed enantioselective allylic alkylation of malonates 2
To a solution of [Pd(η3-C3H5)Cl]2 (0.9 mg, 0.0025 mmol), n-tributyl phosphine (1 mL, 0.005 mmol), and rac-1,3-diphenyl-2-enyl acetate (1, 25.2 mg, 0.1 mmol) in mesitylene (0.5 mL) were successively added Rb2CO3 (184.7 mg, 0.8 mmol), chiral ammonium salt VIII (6.1 mg, 0.01 mmol), and malonate (2, 0.2 mmol) at room temperature. After being stirred vigorously for 48 h, the reaction mixture was diluted with ethyl acetate (20 mL). The organic phase was washed with water (2 × 10 mL) and brine (10 mL). The extract was dried over MgSO4, filtered, and concentrated in vacuo. The crude product was purified by column chromatography (silica gel, ethyl acetate : benzene : hexane = 1:1:12) to give alkylated products 3.