170730-06-0

1-(2,3-Dihydro-7-benzofuranyl)ethanone is an impurity in the synthesis of Darifenacin (D193400, HBr); a medication used to treat urinary incontinence. It works by blocking the M3 muscarinic acetylcholine receptor.

General procedure: N-methoxy-N-methyl-2,3-dihydrobenzofuran-7-carboxylate 1b (10.9 g, 52.65 mmol) was dissolved in 150 mL of anhydrous tetrahydrofuran and degassed three times under argon protection. Subsequently, methylmagnesium bromide solution (35 mL, 3.0 M in diethyl ether, 105 mmol) was slowly added dropwise and the reaction was stirred at room temperature for 1 h to ensure complete reaction. Upon completion of the reaction, the solvent was removed by distillation under reduced pressure. The pH was adjusted to 3-4 by slow dropwise addition of 1 M hydrochloric acid solution to the residue. extraction was carried out with ethyl acetate (30 mL x 4), the organic phases were combined and washed with saturated sodium chloride solution. The organic layer was dried with anhydrous magnesium sulfate, filtered and the filtrate was concentrated under reduced pressure. The residue was purified by silica gel column chromatography with gradient elution using elution system B. The target product 1-(2,3-dihydrobenzofuran-7-yl)ethanone 1c (6.218 g, light yellow solid) was obtained in 73.1% yield.

[1] Patent: CN103382206, 2016, B. Location in patent: Paragraph 0176-0179; 0184-0186