diethylzinc in ethylene glycol dimethyl ether; dichloromethane under Ar; 1) Et2Zn, CH2I2, CH2Cl2/DME, below -10°C, ca. 20 min; 2) to alkene, chiral 1,3,2-dioxoborolane and MS 4A added Zn(CH2I)2/DME complex (from 1)) at below -15°C (20 min), then stirring at -10°C (2 h) and at room temp. (20 h); quenching (satd. aq. NH4Cl), extn. (ether), treatment with 5 M KOH (9 hat room temp.), washing (10percent HCl, satd. NaHCO3, water, brine), drying (mgSO4), flash column chromy. (SiO2, hexane/ethyl acetate = 10:1);

Zn(CH2I)2 in dichloromethane (inert atm.); room temp., 2 h; 90percent enantiomeric purity;

Zn(CH2I)2 in dichloromethane (inert atm.); room temp., 2 h; 90percent enantiomeric purity;

1.1: 1,1'-azobis (cyclohexanecarbonitrile) / 2.5 h / 80 °C 2.1: diethylzinc / dichloromethane; ethylene glycol dimethyl ether / 1 h / -13 - -10 °C / Inert atmosphere 2.2: -10 - 20 °C / Inert atmosphere View Scheme