Dimethylamine → 7-[2-(2,2-Dimethyl-4-trifluoromethyl-[1,3]dioxolan-4-yl)-1,1-dimethyl-ethyl]-2,3-dihydrobenzofuran-5-sulfonic acid dimethylamide

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Reaction Steps

A solution of 5-bromo-7-[2-(2,2-dimethyl-4-trifluoromethyl-[1,3]dioxolan-4-yl)-1,1-dimethylethyl]-2,3-dihydrobenzofuran (4.0 g, 9.4 mmol) in 8 mL of THF was treated with n-BuLi (2.5 M in hexanes, 4.2 mL, 10.5 mmol) at −78° C. After 15 minutes, an excess of SO2 gas was bubbled into the mixture and the reaction was monitored for the disappearance of the starting material. Next, the reaction mixture was concentrated under a stream of nitrogen gas, diluted with THF, and treated with N-chlorosuccinimide (1.48 g, 11.1 mmol). The mixture was stirred for 15 minutes and divided into three equal portions. A stock solution of sulfonyl chloride (⅓ of the mixture) in 8 mL of THF was treated with dimethylamine (2 M in THF, 10 mL, 20 mmol). After 30 minutes, the mixture was diluted with 20 mL of saturated aqueous ammonium chloride solution and extracted with three 10 mL portions of ethyl acetate. The combined organic layers were washed with three 10 mL portions of saturated aqueous ammonium chloride solution, two 10 mL portions of brine, dried over magnesium sulfate, filtered, and concentrated in vacuo. The crude material was purified on silica gel (3% to 30% ethyl acetate in hexanes, gradient) to afford 1.18 g (83% yield) of 7-[2-(2,2-dimethyl-4-trifluoromethyl-[1,3]dioxolan-4-yl)-1,1-dimethyl-ethyl]-2,3-dihydrobenzofuran-5-sulfonic acid dimethylamide, which was used without further purification.

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