Methanol → (1R)-2-bromo-1-phenylethanol

Participants

Reaction Steps

(R)-2-amino-2-cyclohexyl-1,1-diphenylethanol (59 mg, 0.2 mmol), dry tetrahydrofuran (2 mL) and borane dimethylsulfide complex (100 μL, 1.0 mmol) were added to a dry flask under an atmosphere of nitrogen. The reaction mixture was stirred at room temperature for 1.5 hr to form (R)-4-cyclohexyl-5,5-diphenyl-1,3,2-oxazaborolidine. A solution of bromoacetophenone (199 mg, 1.0 mmol) in dry tetrahydrofuran (4 mL) was added to the borane/(R)-4-cyclohexyl-5,5-diphenyl-1,3,2-oxazaborolidine complex at the rate of 9 mL/hr by means of a syringe pump. The resulting mixture was stirred at room temperature for an additional 1.5 hr. Methanol was added to quench the reaction and then the solvent was removed by evaporation. The resulting residue was chromatographed on silica gel (hexane/ethyl acetate, 25:1) and combination of the like fractions, followed by removal of the solvent gave (R)-2-bromo-1-phenylethanol (170 mg, 97.9% ee). The enantiomeric excess was measured by HPLC (Chiralcel OD-H column, mobile phase, hexane/2-propanol 9:1, flow rate=0.7 mL/min).

Provenance & Evidence