Trimethyl borate → HCID 69930837, compound

Participants

Reaction Steps

(S)-2-amino-2-cyclohexyl-1,1-bis-(4-methoxyphenyl)ethanol (71.1 mg, 0.2 mmol), dry tetrahydrofuran (2 mL) and trimethylborate (27.2 μL, 0.24mmol) were added to a dry flask and stirred under an atmosphere of nitrogen for 1.5 hours to form a solution of (S)-4-cyclohexyl-5,5-bis-(4-methoxyphenyl)-2-methoxy-1,3,2-oxazaborolidine. Borane dimethylsulfide complex (100 μL, 1.0 mmol) was added to this solution and the mixture was stirred at room temperature for a further 30 minutes. A solution of 3,5-(bistrifluoromethyl)-acetophenone (180 μL, 1.0 mmol) in tetrahydrofuran (3 mL) was added by means of a syringe pump at a rate of 9 mL/min and the reaction then stirred for a further 1.5 hours. Thin layer chromatography (silica gelhexane/ethyl acetate 4:1) showed no starting material. The reaction was quenched by addition of methanol. The solvent was evaporated under vacuum and the residue was dissolved in ethyl acetate and washed 3 times with 1N HCl. The ethyl acetate solution was dried over magnesium sulfate, filtered through a plug of silica gel and concentrated to give (R)-1-[3,5-(bistrifluoromethyl)phenylethanol. The enantiomer ratio was determined by HPLC using a Chiralcel OD 25 cm×4.6 mm column with hexane/2-propanol (97: 3) mobile phase at 0.7 mL/min at 25° C. Detection with UV was at 254 nm.

Provenance & Evidence