Iodine → (2R)-1-(2,5-Difluorophenyl)-2-((tetrahydro-2H-pyran-2-yl)oxy)propan-1-one

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A mixture of magnesium (7.25 g, 0.298 mol) and iodine (catalytic amount) and 1-bromo-2,5-difluorobenzene (20.0 g, 0.178 mol) in THF (250 ml) was vigorously stirred. The color of iodine was disappeared and the inner temperature rose up to 65° C. To this mixture was added additional 1-bromo-2,5-difluorobenzene (30.0 g, 0.267 mol) dropwise to maintain the inner temperature from 50 to 55° C. over 45 min. The resulting mixture was stirred at 55° C. for 30 min. then at r.t. for 1 hr. The mixture was cooled down to −5° C. To this mixture was added a solution of 4-[(2R)-2-(3,4,5,6-Tetrahydro-2H-pyran-2-yloxy)propionyl]morpholine (52.5 g, 0.216 mol) in THF (150 ml) dropwise over 40 min. And the resulting mixture was stirred at r.t. for 4 hrs. The reaction mixture was cooled down to 5° C. and saturated NH4Cl aq. (100 ml) was added carefully. The whole was diluted with H2O (600 ml) and extracted with EtOAc (400 ml+200 ml×2). The combined organic layer was dried over Na2SO4 and concentrated in vacuo. The residue was chromatographed on silica gel (n-hexane:EtOAc=10:1˜5:1) to give (2R)-2′,5′-Difluoro-2-(3,4,5,6-tetrahydro-2H-pyran-2-yloxy)-propiophenone (47.3 g, 81%) as pale yellow syrup.

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