Br[C:2]1[CH:7]=[C:6]([F:8])[C:5]([Cl:9])=[CH:4][C:3]=1[F:10].C([Mg]Br)(C)C.C(O[B:20]1[O:24][C:23]([CH3:26])([CH3:25])[C:22]([CH3:28])([CH3:27])[O:21]1)(C)C.[Cl-].[NH4+]>C1COCC1>[Cl:9][C:5]1[C:6]([F:8])=[CH:7][C:2]([B:20]2[O:24][C:23]([CH3:26])([CH3:25])[C:22]([CH3:28])([CH3:27])[O:21]2)=[C:3]([F:10])[CH:4]=1
To a solution of 1-bromo-4-chloro-2,5-difluorobenzene (200 mg, 0.879 mmol) in THF (10 mL) cooled to −10° C. was added isopropylmagnesium bromide (1M in THF, 1.055 mL, 1.055 mmol) dropwise and the reaction mixture was stirred at this temperature for 1 h. The reaction mixture was then warmed to 0° C. and stirred for another 1 h. The resultant mixture was again cooled to −10° C. and treated dropwise with a solution of 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (196 mg, 1.055 mmol). The reaction mixture was allowed to warm up to room temperature and treated with a saturated solution of ammonium chloride (3 mL). The layers were separated and aqueous layer was extracted with dichloromethane (2×2 mL). The combined organic layer was dried over sodium sulfate, filtered and concentrated under reduced pressure to afford crude compound which was purified by column chromatography on a silica (7:3-Ethyl acetate:hexane) to afford 2-(4-chloro-2,5-difluorophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (150 mg, 0.546 mmol, 62% yield) as an oil. 1H NMR (400 MHz, DMSO-d6) δ ppm 7.46-7.49 (m, 1H), 7.09-7.13 (m, 1H), 1.35 (s, 12H).
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