Chlorine → 4-(5-Chloro-2,3-dihydrobenzofuran-7-yl)-1,1,1-trifluoro-4-methylpentan-2-one

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Reaction Steps

A solution of 4-(2,3-dihydrobenzofuran-7-yl)-1,1,1-trifluoro-4-methylpentan-2-one (20.8 g, 76.2 mmol) in 200 mL of acetic acid was treated with a solution of chlorine gas (Cl2) in acetic acid (prepared by bubbling chlorine gas into acetic acid, ˜1.19 M). The reaction was monitored by 1H-NMR. The ratio of the starting material to product was determined based on the integration of CH2 signal of the respective ketones (starting material: δ=3.32 ppm; product: δ=3.32 ppm). The concentration of the Cl2 solution was recalculated based on the NMR ratios and an additional portion of Cl2 solution was added (this process was repeated until NMR showed the complete consumption of the starting material). The mixture was quenched with 500 mL of water and solid sodium bicarbonate (˜500 g) was added carefully during 1 hour. The mixture was poured onto 500 mL of ethyl acetate. The phases were separated and the aqueous layer was extracted with three 500 mL portions of ethyl acetate. The combined organic layers were washed with two 100 mL portions of brine, dried over magnesium sulfate, filtered, and concentrated in vacuo to afford 23.4 g of the title product (quantitative yield), which was used without purification.

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