[H-].[Na+].[C:3]([CH:8]1[CH2:12][CH2:11][CH2:10][C:9]1=[O:13])([O:5][CH2:6][CH3:7])=[O:4].[F:14]N1CC2CCC(C2(C)C)(C)CS1(=O)=O.C(O)(=O)C(O)=O>O1CCCC1>[F:14][C:8]1([C:3]([O:5][CH2:6][CH3:7])=[O:4])[CH2:12][CH2:11][CH2:10][C:9]1=[O:13]To a suspension of 1.56 mmol of sodium hydride in 5 ml of tetrahydrofuran are added, at 0° C., 1.3 mmol of 1-carboethoxycyclopentan-2-one and the mixture is stirred for 1 hour at 0° C. Then a solution of 1.4 mmol of (-)-N-fluorocamphor sultam (Example 4) is added dropwise, and stirring is continued for 3 hours at 0° C. The reaction mixture is then poured into 50 ml of 1M oxalic acid and extracted with diethyl ether. The organic phases are washed with 10% NaHCO3 solution and with a saturated solution of NaCl. The resultant mixture is purified over a column of silica gel, affording (+)-1-fluoro-1-carboethoxycyclopentan-2-one in high purity (ee=70%).
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