C([Li])CCC.Br[C:7]1[CH2:11][CH2:10][CH2:9][C:8]=1[C:12]1[CH:17]=[C:16]([Cl:18])[CH:15]=[CH:14][C:13]=1[O:19][CH2:20][C:21]1[CH:26]=[CH:25][CH:24]=[CH:23][CH:22]=1.[B:27](OC(C)C)([O:32]C(C)C)[O:28]C(C)C.Cl>O1CCCC1.CCOCC>[CH2:20]([O:19][C:13]1[CH:14]=[CH:15][C:16]([Cl:18])=[CH:17][C:12]=1[C:8]1[CH2:9][CH2:10][CH2:11][C:7]=1[B:27]([OH:32])[OH:28])[C:21]1[CH:26]=[CH:25][CH:24]=[CH:23][CH:22]=1A solution of n-butyllithium (0.73 ml, 1.6M in hexanes, 1.17 mmol) was added to a solution of 1-bromo-2-(2-benzyloxy-5-chlorophenyl)cyclopentene (424 mg, 1.17 mmol) in anhydrous tetrahydrofuran (12 ml) at −78° C. under nitrogen. The resulting solution was stirred for 15 minutes and triisopropyl borate (440 mg, 2.34 mmol) was added. The mixture was allowed to warm to room temperature, 1M hydrochloric acid (20 ml) was added and stirred vigorously for 15 minutes. After diluting with ether the organic phase was dried (magnesium sulphate), evaporated and purified by chromatography on silica (1:4 ethyl acetate/iso-hexane) to give the title compound as a white solid (214 mg, 58%). LC/MS: Rt 3.4, [2 MH−] 637.3.
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