chiral oxazaborolidine prepared from (S)-α,α-diphenyl-2-pyrrolidinemethanol and Me3SiCH2B(OH)2; benzo[1,3,2]dioxaborole in toluene T=-78°C;

1: 1.) n-BuLi / 1.) THF, -78 deg C, 2.) THF, from -78 deg C to 23 deg C 2: AlCl3 / CH2Cl2 / 0 °C 3: 95 percent / chiral oxazaborolidine prepared from (S)-α,α-diphenyl-2-pyrrolidinemethanol and Me3SiCH2B(OH)2, catecholborane / toluene / -78 °C View Scheme

1: AlCl3 / CH2Cl2 / 0 °C 2: 95 percent / chiral oxazaborolidine prepared from (S)-α,α-diphenyl-2-pyrrolidinemethanol and Me3SiCH2B(OH)2, catecholborane / toluene / -78 °C View Scheme

1.1: n-butyllithium / tetrahydrofuran; hexane / 0.5 h / -40 °C / Inert atmosphere 1.2: 0.5 h / -40 °C 2.1: manganese(IV) oxide / dichloromethane / 12 h / 20 °C / Inert atmosphere 3.1: [(R,R)-N-(p-toluenesulfonyl)-1,2-diphenylethylenediamine](p-cymene)ruthenium / dichloromethane; isopropyl alcohol / 1.5 h / Inert atmosphere View Scheme

[(R,R)-N-(p-toluenesulfonyl)-1,2-diphenylethylenediamine](p-cymene)ruthenium in dichloromethane; isopropyl alcohol 1.5 h; Inert atmosphere; optical yield given as percent ee;

1: manganese(IV) oxide / dichloromethane / 12 h / 20 °C / Inert atmosphere 2: [(R,R)-N-(p-toluenesulfonyl)-1,2-diphenylethylenediamine](p-cymene)ruthenium / dichloromethane; isopropyl alcohol / 1.5 h / Inert atmosphere View Scheme