Ethyl Acetate → 2-(2,4-Dichloro-benzoyl)-6-hydroxy-benzofuran-3-carboxylic acid ethyl ester

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To a solution of [4-(tert-Butyl-dimethyl-silanyloxy)-2-hydroxy-phenyl]-oxo-acetic acid ethyl ester from step 2 (2.0 g, 6.16 mmol) and 2-chloro-1-(2,4-dichlorophenyl)ethanone (1.65 g, 7.4 mmol, 1.2 eq) in anhydrous N,N-dimethylformamide (100 mL) was added potassium carbonate (1.7 g, 12.3 mmol, 2 eq). The reaction mixture was stirred at 90° C. for 16 h. The mixture was cooled to room temperature then poured into ethyl acetate (100 mL) and water (100 mL). The aqueous layer was extracted with ethyl acetate (2×100 mL). Combined the organic layer was washed by water (2×100 mL), dried over Na2SO4, filtrated, and evaporated in vacuo. The residue was purified by column chromatography eluted with 20% EtOAc/hexane then 50% EtOAc/hexane solution to afford an yellow solid (843 mg, 36%) as product. 1H-NMR (CD3CN): δ 7.79 (d, J=8.0 Hz, 1H), 7.64 (d, 1.9 Hz, 1H), 7.59 (d, J=8.0 Hz, 1H), 7.47(dd, J=2.3, 8.3 Hz, 1H), 7.06 (d, J=2.3 Hz, 1H), 7.0 (dd, J=2.3, 8.0 Hz, 1H), 4.11(q, 2H), 1.21(t, 3H).; LC-MS (MH+=379/381).

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