Br[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][C:3]=1[F:8].[O:9]1[CH2:14][CH2:13][CH2:12][CH2:11][CH:10]1[O:15][C@@H:16]([CH3:25])[C:17](N1CCOCC1)=[O:18].[Mg].[Cl-].[NH4+]>O1CCCC1.O>[F:8][C:3]1[CH:4]=[CH:5][CH:6]=[CH:7][C:2]=1[C:17](=[O:18])[C@@H:16]([O:15][CH:10]1[CH2:11][CH2:12][CH2:13][CH2:14][O:9]1)[CH3:25]
1-Bromo-2-fluorobenzene (15 g) and 40 g of 4-[(2S)-2-(3,4,5,6-tetrahydro-2H-pyran-2-yloxy)propionyl]morpholine was dissolved in 200 ml of tetrahydrofuran, to which 44 g of magnesium turnings was added, and the mixture was vigorously stirred. The reaction vessel was cooled when a temperature of the reaction solution was raised to 35° C., and 16.7 g of 1-bromo-2-fluorobenzene was added dropwise to the reaction solution at 35° to 37° C. over the period of 10 minutes. After stirring at 30° to 35° C. for 2 hours, the reaction solution was ice-cooled, to which 100 ml of a saturated aqueous solution of ammonium chloride and 100 ml of water were added. The mixture was extracted with ethyl acetate (200 ml×2, 100 ml). Then, the extract was washed with water and an aqueous solution of sodium chloride successively, and dried over magnesium sulfate. The solvent was distilled off under reduced pressure and the residue was purified by silica gel chromatography (eluent; hexane:ethyl acetate=10:1 to 5:1) to give 22.4 g of (2S)-2'-fluoro-2-(3,4,5,6-tetrahydro-2H-pyran-2-yloxy)propiophenone as a pale yellow oil.
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