Water → (S)-N-[2-(4-chlorophenyl)-2-cyclopropylacetyl]-4-(1-methylethyl)-2-oxazolidinone

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In a separate reaction vessel a stirred solution of 2.0 grams (0.016 mole) of (S)-4-(1-methylethyl)-2-oxazolidinone in 50 mL of tetrahydrofuran was cooled to -78° C., and 6.25 mL (0.016 mole) of n-butyllithium (2.5 molar in hexane) was added dropwise. Upon completion of addition, the reaction mixture was stirred for 30 minutes, and then the 2-cyclopropyl-2-(4-chlorophenyl)acetyl chloride, prepared above, was added dropwise during several minutes. Upon completion of addition, the reaction mixture was stirred for an additional 30 minutes and then was poured into water. The organic layer was separated and washed with one portion of aqueous sodium bicarbonate. The organic layer was dried with magnesium sulfate and filtered. The filtrate was concentrated under reduced pressure to a residual oil. The oil was subjected to chromatography on silica gel using hexane:diethyl ether (3:1) as eluant. The appropriate fractions were combined and concentrated under reduced pressure, yielding 0.85 gram of diastereomer (A) and 0.8 gram of diastereomer (B) of (S)-N-[2-(4-chlorophenyl)-2-cyclopropylacetyl]-4-(1-methylethyl)-2-oxazolidinone. Upon standing, diastereomer (A) crystallized to a solid, m.p. 61°-64° C.

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