7-Bromobenzo[b]furan

Scheme I, 1-Bromo-2-(2, 2-diethoxyethoxy)benzene (0102-3)(3.33g, 11.56mol, 1.0 equivalent)Soluble in DCE (60ml), add PPA(11.72g, 34.68mmol, 3.0 equivalents), The air in the round bottom flask was replaced with nitrogen three times and then refluxed at 83 ° C for 3 hours.After the reaction was completed, dichloromethane (100 ml) was added, and water (100 ml × 3) was washed.The organic phase was dried over anhydrous sodium sulfate and concentrated.Then purified by silica gel column chromatography (petroleum ether = 100percent) to give pale-yellow solid product 7-bromobenzofuran(1.336 g, yield: 58percent).A stirred mixture of polyphosphoric acid (~5 g) and chlorobenzene (8 mL) was heated at reflux and a solution of l-(2, 2-diethoxyelhoxy)-2-bromobenzene (2.62 g, 9.0 mmol) in chlorobenzene (3 mL) was added dropwise over 10 min. The mixture was heated at reflux for 1.5 h. The mixture was allowed to cool to rt and IM aq NaOH (20 mL) was added, followed by ether (175 mL). The mixture was washed with water (2 x 20 mL) and brine (20 mL), and dried over MgSOPreparation of 7-Bromobenzo(b)furan 1) In a dry 500mL three-necked flask, add 4-bromoaniline (17.20g, 100mmol) and 7-Bromobenzofuran (0103-3) (1.06 g, 5.36 mmol, 1.0 eq.) was dissolved in EtOAc (10 mL).Add butyl vinyl ether (0.698 g, 6.97 mmol, 1.3 equivalents), Palladium acetate (0.12 g, 0.536 mmol, 0.1 equivalent), DPPP (0.221 g, 0.536 mmol, 0.1 equivalent), TEA (1.08 g, 10.71 mmol, 2.0 eq.), The reaction solution was reacted at 150 C for 1 hour in a nitrogen-filled sealed tube.After the reaction was completed, it was diluted with ethyl acetate (50 ml) and washed with water (100 ml × 3).The organic phase is dried over anhydrous sodium sulfate.After concentration, it was dissolved in tetrahydrofuran (15 ml).Add 1 M HCl (12 ml) for 3 hours at room temperature.After the reaction was completed, it was extracted with ethyl acetate (100 ml).The organic phase is dried over anhydrous sodium sulfate.After concentration, it was purified by silica gel column chromatography ( petroleum ether: ethyl acetate = 10:1)The pale yellow solid product 1-(benzofuran-7-yl)ethanone (0.79 g, yield: 92%).