Cyclopentanone → Ethyl 6-amino-5-bromo-2-(1-hydroxycyclopentyl)benzofuran-3-carboxylate

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Reaction Steps

To a solution of LDA (6.32 g, 59.0 mmol) in THF (60 mL) was added dropwise ethyl 6-amino-5-bromobenzofuran-3-carboxylate (5 g, 17.6 mmol) at −78° C. under N2. After the mixture was stirred for 1 hour, cyclopentanone (4.44 g, 52.8 mmol) in THF (40 mL) was added dropwise at −78° C. After the mixture was stirred for 1 h, NH4Cl (a.q.) was added, then the mixture was extracted with EtOAc (100 mL*3) and dried over Na2SO4 After concentration, the residue was purified by column chromatography (PE:EtOAc=10:1) to give the product of ethyl 6-amino-5-bromo-2-(1-hydroxycyclopentyl)benzofuran-3-carboxylate (2.9 g, yield: 44%). 1H-NMR (CDCl3, 400 MHz) δ 7.94 (s, 1H), 6.86 (s, 1H), 6.07 (s, 1H), 4.46 (q, J=7.2 Hz, 2H), 4.20 (s, 1H), 2.12˜2.17 (m, 4H), 1.99 (t, J=5.6 Hz, 2H), 1.79 (t, J=3.2 Hz, 2H), 1.50 (t, J=7.2 Hz, 3H). MS (M+H)+: 368/370.

Provenance & Evidence