2-Chloro-3-ethylbenzoxazolium Tetrafluoroborate

Experimental procedure: To a stirred suspension of 2-chloro-3-ethylbenzoxazolium tetrafluoroborate (1.3 mmol) and tetraethylammonium chloride (1.0 mmol) in dichloromethane (2 mL) cooled to 0 °C is added triethylamine (1.3 mmol) in dichloromethane (1 mL) under an argon atmosphere. To the yellow suspension is added dropwise 3β-cholestanol (1.0 mmol) in dichloromethane (1.5 mL) and the resulting mixture is stirred at the same temperature for additional 4 h. After evaporation of the solvent reduced pressure, the residue is directly chromatographed on silica gel eluting with hexane to give 1 in 85% yield.