N-benzyl-4-fluorophenyl-1,4-oxazin-2-one → N-benzyl-3-(S)-(4-fluorophenyl)-1,4-oxazin-2-one

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Reaction Steps

To a solution of N-benzyl-4-fluorophenyl-1,4-oxazin-2-one (10 g) in isopropyl acetate (110 ml) at room temperature was added a solution of (-)-3-bromocamphor-8-sulphonic acid ((-)-3-BCS) (12 g) in acetonitrile (24 ml). Crystallisation began after 2-3 minutes. The slurry was stirred for 1 hour at room temperature. Trifluoroacetic acid (7 ml) was added and the mixture stirred at 65° C. for 3 days. The mixture was cooled to 0°-5° C., aged for 1 hour and the solid collected, washed with isopropyl acetate and dried in vacuo at 40° C., to give the N-benzyl-3-(S)-(4-fluorophenyl)-1,4-oxazin-2-one (-)-3-BCS salt: yield 17.24 g, ee 98.6% (S) isomer.

Provenance & Evidence