Br[CH2:2][CH2:3]Br.[Br:5][C:6]1[CH:11]=[C:10]([Cl:12])[CH:9]=[C:8]([OH:13])[C:7]=1[OH:14].[OH-].[Na+]>[Br-].C([N+](CCCC)(CCCC)CCCC)CCC.O>[Br:5][C:6]1[C:7]2[O:14][CH2:3][CH2:2][O:13][C:8]=2[CH:9]=[C:10]([Cl:12])[CH:11]=1
To a solution of 1,2-dibromoethane (1.44 ml, 16 mmol) and tetrabutylammonium bromide (96 mg, 2.5 mol %) in water (8 ml) at reflux under nitrogen was added a mixture of 3-bromo-5-chloro-benzene-1,2-diol (Preparation 21, 2.68 g, 12 mmol) and NaOH (1.06 g, 26.2 mmol) in water (10 ml) over 4 hours, and the resultant mixture stirred overnight. The reaction mixture was cooled to room temperature and diluted with water (100 ml). The mixture was extracted with Et2O (3×100 ml), and the combined organic extracts were concentrated in vacuo. Purification by flash chromatography (pentane:dichloromethane 9:1) afforded the desired product as a yellow oil (1.78 g, 60%) which crystallised on standing to a yellow solid.
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