[Mg].Br[C:3]1[CH:8]=[CH:7][CH:6]=[C:5]([F:9])[CH:4]=1.BrCCBr.[Si:14]([O:21][CH2:22][C:23](N(OC)C)=[O:24])([C:17]([CH3:20])([CH3:19])[CH3:18])([CH3:16])[CH3:15]>>[Si:14]([O:21][CH2:22][C:23]([C:3]1[CH:8]=[CH:7][CH:6]=[C:5]([F:9])[CH:4]=1)=[O:24])([C:17]([CH3:20])([CH3:19])[CH3:18])([CH3:16])[CH3:15]To a suspension of magnesium turnings (2.10 g, 85.7 mmol) in anhydrous THY (120 mL), was added slowly at RT 1-bromo-3-fluorobenzene (10.0 g, 57.2 mmol) and 1,2-dibromoethane (0.10 mL). After stirring for 40 min under argon, the mixture was cooled to −78° C., and 2-(tert-butyldimethylsilyloxy)-N-methoxy-N-methylacetamide (9.3 g, 40 mmol) was added. The resulting mixture was warmed to 0° C. and stirred for 2 h. The reaction was quenched with saturated NH4Cl (5.0 mL), and the insoluble material was filtered. The filtrate was dried (Na2SO4), filtered and concentrated in vacuo. The residue was purified by SiO2 chromatography eluting with petroleum ether/EtOAc (20:1) to afford 10.3 g (93%) of 2-(tert-butyldimethylsilyloxy)-1-(3-fluorophenyl)ethanone (58a) as oil. LCMS (ESI) m/z: 268.0[M+H]+.
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