Br[C:2]1[C:10]2[S:9][CH:8]=[CH:7][C:6]=2[CH:5]=[CH:4][CH:3]=1.C([Li])CCC.CCCCCC.[B:22](OC)([O:25]C)[O:23]C>CCOCC>[S:9]1[C:10]2[C:2]([B:22]([OH:25])[OH:23])=[CH:3][CH:4]=[CH:5][C:6]=2[CH:7]=[CH:8]1A solution of 7-bromo-1-benzothiophene (19.9 g, 0.094 mol) in absolute ether (200 ml) was treated with a 1.6 M solution of n-butyllithium in hexane (0.14 mol, 88 ml) at −78° C. The solution was stiffed at −78° C. for 10 minutes then treated with trimethyl borate (15 ml, 0.14 mol). The mixture was allowed to warm to −10° C. then quenched with an excess of dilute hydrochloric acid. The organic layer was separated, dried, evaporated, and the residue was recrystallised from aqueous ethanol to yield the title compound (10 g, 60%).
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