(R)-2-Methyl-CBS-oxazaborolidine → Trifluoromethanesulfonic acid 5-hydroxy-5,6,7,8-tetrahydronaphthalen-2-yl ester

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Reaction Conditions

Reaction Steps

To a dry three-necked flask containing (R)-2-methyl-CBS-oxazaborolidine (Aldrich, 1.94 mL, 1.0 M in toluene, 1.93 mmol, 0.05 eq) under N2 was added a solution of borane-methylsulfide (BMS) (Aldrich, 3.30 mL, 34.80 mmol, 0.9 eq) in toluene (200 mL) through an additional funnel at RT. After the addition, the reaction was cooled to 0° C. A solution of trifluoro-methanesulfonic acid 5-oxo-5,6,7,8-tetrahydro-naphthalen-2-yl ester (11.37 g, 38.67 mmol, 1.0 eq) in THF (180 mL) was added drop-wise through an additional funnel. Following the addition, the reaction was warmed to RT and stirred for additional 40 min, then quenched with MeOH. The solvent was removed in vacuo. The residue was treated with H2O (50 mL), and extracted with ether (3×150 mL). The combined organic layers were washed with brine, dried over Na2SO4, filtered and concentrated in vacuo. The title compound was obtained as an off-white solid after flash chromatography purification (16–22% EtOAc-hexane).

Provenance & Evidence