tert-Butyl[4-(dimethoxymethyl)phenoxy]dimethylsilane

Typical Procedure
(Protection of Diols):
A 500-mL, oven-dried, three-necked round-bottomed flask equipped with a reflux condenser (fitted with an argon gas inlet), a teflon-coated magnetic stir bar, a rubber septum, and a thermocouple is charged with (R,R)-(+)-1,2-diphenyl-1,2-ethanediol (6.43 g, 30.0 mmol), toluene (96 mL), CH₃CN (32 mL), and tert-butyl[4-(dimethoxymethyl)phenoxy]dimethylsilane (9.27 g, 32.8 mmol). After stirring the solution for 3 min, PPTS (2.26 g, 9.0 mmol) is added. The reaction mixture is heated in a 50 °C oil bath (internal temperature: 45 °C) and is stirred for 1 h. The mixture is cooled to ambient temperature and then is poured into sat. aq. NaHCO₃ solution (100 mL) in a 1-L separatory funnel, and the suspension is extracted with EtOAc (3 × 100 mL). The combined organic extracts are washed with sat. aq. NaCl solution (2 × 100 mL), then are dried over anhydrous Na₂SO₄ (20 g), filtered, and concentrated on a rotary evaporator under reduced pressure to give a yellow, viscous oil. The residue is purified by silica gel column chromatography (hexane : CH₂Cl₂ = 7 : 3) to give a colorless, viscous oil (12.33 g) which is triturated with MeOH to yield the product as a white solid (11.51 g, 89%).
(Deprotection): A 500-mL, three-necked round-bottomed flask equipped with a reflux condenser (fitted with an argon inlet), a teflon-coated magnetic stir bar, a rubber septum, and a thermocouple is charged with the protected compound (10.8 g, 25.0 mmol), K₂CO₃ (17.3 g, 125 mmol), MeOH (200 mL), and water (50 mL). After addition of KF (1.46 g, 25.0 mmol) and stirring for 5 min followed by addition of NH₂OH.HCl (8.69 g, 125 mmol), the reaction mixture is heated in an 85 °C oil bath (internal temperature: 69 °C) and is stirred for 37 h. The reaction mixture is cooled to ambient temperature and is decanted into sat. brine (150 mL) in a 1-L separatory funnel and is extracted with EtOAc (3 × 200 mL). The combined organic extracts are washed with 3 M NaOH (3 × 100 mL), H₂O (100 mL), and brine (100 mL), and then are dried over anhydrous Na₂SO₄ (20 g), filtered, and concentrated on a rotary evaporator (21 °C 30 mmHg) to afford 5.40 g of the crude diol as a white solid. Purification by recrystallization yields (R,R)-(+)-1,2-diphenyl-1,2-ethanediol as white crystals (4.65 g, 87%).