Sulfuric Acid → Ethyl 7-(4-ethylphenyl)-2,3-dihydro-1-benzoxepine-4-carboxylate

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Reaction Steps

Under argon atmosphere, to a solution of 4-ethylbromobenzene (10.0 g) in tetrahydrofuran (60 ml) was added n-butyllithium (1.6M hexane solution) (37.2 ml) at −78° C., and the mixture was stirred for 1 hour. To the reaction mixture was dropwise added a solution of tributyl borate (13.68 g) in tetrahydrofuran (30 ml), and the reaction mixture was warmed to room temperature and stirred at room temperature for 2 hours. To the reaction mixture was added 10% sulfuric acid (100 ml), and the mixture was stirred for 1 hour. The mixture was extracted with ethyl acetate. The organic layer was washed with saturated sodium chloride solution, dried with magnesium sulfate and concentrated under reduced pressure. The residue was dissolved in acetone (30 ml), and to the mixture was added 10% sulfuric acid (50 ml). The mixture was stirred at room temperature for 16 hours, and under reduced pressure acetone was evaporated. The mixture was extracted with ethyl acetate. The organic layer was washed with saturated sodium chloride solution, dried with magnesium sulfate and concentrated under reduced pressure. The residue was separated and purified with column chromatography (ethyl acetate/hexane=1:2) to give crude 4-ethylphenyl borate (0.91 g) as colorless solid. Under argon atmosphere, a solution of ethyl 7-bromo-2,3-dihydro-1-benzoxepine-4-carboxylate (500 mg), the above crude 4-ethylphenyl borate (0.32 g) and potassium carbonate (0.49 g) in toluene-ethanol-water (20-2-2 ml) was stirred at room temperature for 1 hour. To the reaction mixture was added tetrakistriphenyl-phosphinepalladium (0.06 g), and the mixture was refluxed for 18 hours and cooled to room temperature. The organic layer was washed with saturated sodium chloride solution, dried with magnesium sulfate and concentrated under reduced pressure. The residue was separated and purified with column chromatography (ethyl acetate/hexane=1:15) to give ethyl 7-(4-ethylphenyl)-2,3-dihydro-1-benzoxepine-4-carboxylate (464 mg) as colorless crystals.

Provenance & Evidence