Benzenesulfonic acid, 4-methyl-, compd. with pyridine (1:1) → (2R)-1-(2,4-difluorophenyl)-2-hydroxypropan-1-one

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Reaction Conditions

Reaction Steps

(2R)-2′,4′-Difluoro-2-(3,4,5,6-tetrahydro-2H-pyran-2-yloxy)propiophenone (9.62 g, 35.6 mmol, synthesized according to the description in Chem. Pharm. Bull., Vol. 41(6), 1035-1042 (1993)) was dissolved in ethanol (99.5%, 50 mL), and pyridinium p-toluenesulfonate (0.89 g, 3.6 mmol) was added. The mixture was stirred at 50-60° C. for 1 hr. After cooling, the reaction mixture was concentrated under reduced pressure to about 10 mL. Water (20 mL) was flown in and the mixture was extracted twice with ethyl acetate (50 mL). The layers extracted with ethyl acetate were mixed, washed with saturated brine (20 mL) and dried over anhydrous magnesium sulfate. After filtration, the filtrate (ethyl acetate solution) was concentrated. The obtained concentrate (about 9.5 g) was subjected to silica gel column chromatography (SiO2, 30 g) and eluted with n-heptane-ethyl acetate (10:1→5:1). The objective fraction was concentrated to give the title compound as a pale-yellow oil (6.00 g, yield: 91%).

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