Dichloromethane → 6-[2-(5-Chloro-2,4-dimethoxy-phenyl)ethyl]-6-cyclopentyl-tetrahydropyran-2,4-dione

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A solution of 6-[2-(2,4-dimethoxyphenyl)ethyl]-6-cyclopentyldihydro-2H-pyran-2,4(3H)-dione (from example A(39); 4.50 g, 13 mmol) in CH2Cl2 (20 mL) was cooled to −5° C. and treated with a solution of SO2Cl2 (1.94 g, 14.3 mmol) in CH2Cl2 (10 mL) dropwise under nitrogen. The reaction mixture was stirred for an additional 15 minutes at −5° C., then allowed to warm gradually to room temperature. After a total reaction time of 2 h, an aqueous solution of NaHCO3 (5 wt %) was added to achieve a pH of 8 in the aqueous phase. The volatiles were removed in vacuo. The residue was treated with water and extracted with ethyl acetate (3×25 mL). The combined ethyl acetate extract was acidified to a pH 2 using 2 N HCl, then washed with water. The organic phase was dried over Na2SO4, filtered, and concentrated to a yellowish solid. Recrystallization from ether afforded the title product as a white solid (2.18 g, 44%).

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