[Cl:1][C:2]1[C:3]([OH:12])=[CH:4][C:5]2[CH:9]=[CH:8][S:7][C:6]=2[C:10]=1[Cl:11].C([Li])CCC.C(Cl)(Cl)(Cl)Cl.C(=O)=O.[CH3:26][C:27]([CH3:29])=[O:28]>O1CCCC1.C(O)(=O)C.O>[Cl:1][C:2]1[C:3]([OH:12])=[CH:4][C:5]2[CH:9]=[C:8]([C:27]([CH3:29])([CH3:26])[OH:28])[S:7][C:6]=2[C:10]=1[Cl:11]
To a solution of 6,7-dichloro-5-hydroxybenzo[b]thiophene in 28 ml of dried tetrahydrofuran at -28° is added 21 ml of 2.5M n-butyllithium, maintaining the temperature below -18°. Following the addition, the carbon tetrachloride-dry ice bath is replaced with an ice-water bath and the mixture is stirred at 0°-5° for about 4 hrs. A solution of 3.3 ml of acetone in 10 ml tetrahydrofuran is added dropwise. After stirring for one hr, the solution is poured onto 100 ml of water and acidified to pH=5-6 with glacial acetic acid. The acidic solution is extracted with ethyl acetate, washed, dried over anhydrous magnesium sulfate, filtered and the solvent is removed to give 3.84 g of 6,7-dichloro-5-hydroxy-α,α-dimethylbenzo[b]thiophene-2-methanol, mp 171°-173°.
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