Ethanol → (R)-3-(4-chlorophenyl)-1-(phenylmethyl)hexahydropyrazine dihydrochloride

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Reaction Conditions

Reaction Steps

To (R)-2-(4-chlorophenyl)-4-(phenylmethyl)-1-(2-propenyl)hexahydropyrazine (357 mg, 1.1 mmol) produced in Example 15, ethanol (3 mL), distilled water (0.2 mL) and tris(triphenylphosphine) rhodium chloride (30 mg, 0.05 equivalent) were added. The mixture was stirred at 95° C. for 18 hours, and was concentrated. To the concentrate, 1 N hydrochloric acid (5 mL) and toluene (5 mL) were added; and formed insolubles were removed by filtration. After the organic layer and aqueous layer was separated, the obtained aqueous layer (yield: 63%, chemical purity: 77.5 area %, optical purity: 97.7% e.e.) was concentrated. To the concentrate, acetone (10 mL) was added to precipitate crystals. The mixture was stirred at 25° C. for 1 hour, then cooled to 5° C., and further stirred for 1 hour. The crystals were separated by filtration under reduced pressure, then washed with acetone (5 mL), and dried under vacuum, to obtain 134 mg of the title compound as white crystals (yield: 44%, chemical purity: 99.1 area %, optical purity: 99.9% e.e.). The retention time in the chemical purity analysis method was 3.1 min.

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