[S:1]1[CH:5]=[CH:4][C:3]2[C:6](=O)[C:7]3[S:8][CH:9]=[CH:10][C:11]=3[C:12](=[O:13])[C:2]1=2.[BH4-].[Na+].[OH-].[K+].S([O:24][CH3:25])(OC)(=O)=O.[CH2:26](OCC)C>O.C(O)C>[CH3:26][O:13][C:12]1[C:2]2[S:1][CH:5]=[CH:4][C:3]=2[C:6]([O:24][CH3:25])=[C:7]2[S:8][CH:9]=[CH:10][C:11]=12Benzo[1,2-b:4,5-b′]dithiophene-4,8-dione (7.50 g, 34.0 mmol., 1.00 equiv.), ethanol (45 mL) and water (45 mL) were added to a 250 mL 2-neck round-bottom flask fitted with a reflux condenser. NaBH4 (3.89 g, 102 mmol., 3.00 equiv.) was then added portion-wise cautiously. The reaction mixture was heated to reflux for 1 hour. The flask was removed from the heat bath and potassium hydroxide (4.39 g, 78.2 mmol., 2.30 equiv.) was added slowly to the reaction mixture with vigorous stirring. The suspension was stirred at reflux for 30 minutes before adding dimethyl sulfate (16 mL, 170 mmol., 5.0 equiv.), and the suspension was refluxed for 64 hours. The reaction mixture was cooled to room temperature and diluted with water (75 mL) and diethyl ether (500 mL) and more water (300 mL). The organic layer was washed with brine (200 mL), dried with MgSO4 and concentrated. The crude material was purified by silica gel column chromatography (solid loading, gradient of 1:1 to 1:2 hexanes-dichloromethane) to give a white solid (5.314 g, 62% yield). 1H NMR (400 MHz, CDCl3) δ 7.52 (d, J=5.5 Hz, 2H), 7.41 (d, J=5.5 Hz, 2H), 2.81 (d, J=6.7, 2H), 4.15 (s, 6H).
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