4-Nitrobenzoic Acid → (S)-1-[(3R,5R)-5-(3,4,5-trifluorophenyl)morpholine-3-yl]ethanol

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Reaction Steps

Under a nitrogen atmosphere, to a tetrahydrofuran (50 mL) solution containing (R)-1-[(3R,5R)-5-(3,4,5-trifluorophenyl)morpholine-3-yl]ethanol (2.25 g), triphenylphosphine (4.51 g) and 4-nitrobenzoic acid (2.88 g) was dropwise added diisopropyl azodicarboxylate (3.39 mL) while cooling with ice. The resultant solution was stirred at the same temperature for 30 minutes, and then at room temperature for 2 hours. The reaction solution was diluted with water and ethyl acetate, and the organic layer was partitioned. The organic layer was washed with brine, and then dried over anhydrous magnesium sulfate. Solvent was removed by distillation under reduced pressure, and the resulting residue was crudely purified by silica gel column chromatography (heptane/ethyl acetate 8/2→1/1), to thereby obtain a crude product (3.6 g) of 4-nitrobenzoic acid (S)-1-[(3R,5R)-5-(3,4,5-trifluorophenyl)morpholine-3-yl]ethyl ester. A solution of the obtained crude product (3.53 g) in methanol (300 mL) was added sodium methoxide (4.39 mL, 28% methanol solution), and the resultant solution was stirred at room temperature for 1 hour. Solvent was removed by distillation under reduced pressure, and the resultant product was diluted with ethyl acetate and water. The organic layer was partitioned, washed with brine, and then dried over anhydrous magnesium sulfate. Solvent was removed by distillation under reduced pressure, and the resulting residue was purified by silica gel column chromatography (heptane/ethyl acetate 9/1→1/1), to thereby obtain the titled compound (1.19 g). The physical properties of the compound were as follows.

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