3-Bromo-4,5-dimethoxybenzaldehyde → 3,4-Dimethoxy-5-thien-2-yl-benzaldehyde

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Ex-1D: A solution of 5-bromo-3,4-dimethoxybenzaldehyde (10.23 g, 41.7 mmol) in 359 mL of ethylene glycol dimethyl ether was purged with nitrogen gas for 30 min. The solution was treated with tetrakis(triphenylphosphine)palladium(0) (5.0 g, 4.3 mmol), thiophene-2-boronic acid (8.01 g, 62.6 mmol), and a solution of 2 N sodium carbonate 72 mL, 3.45 mmol). The reaction was refluxed for 16 h. The reaction mixture was concentrated, diluted with an aqueous solution of saturated sodium bicarbonate (75 mL), and extracted with dichloromethane (2×100 mL). The organic layer was dried over sodium sulfate and concentrated to a brown solid. The crude material was purified by silica gel chromatography (1:1 ethyl acetate/hexanes) to give 9.42 g (90%) of the desired 3,4-dimethoxy-5-(thien-2-yl)benzaldehyde product. 1H-NMR (300 MHz, CDCl3) δ 9.94 (s, 1H), 7.79 (d, 1H), 7.57 (dd, 1H), 7.41 (d, 1H), 7.36 (d, 1H), 7.13 (dd, 1H), 3.97 (s, 3H), 3.93 (s, 3H).

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