2-Fluorobenzoic acid → 2-Fluoro-5-chlorosulfonylbenzoic acid

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Reaction Steps

o-Fluorobenzoic acid is reacted with chlorosulfonic acid by the method of Example 1 to form 2-fluoro-5-chlorosulfonylbenzoic acid. This is reacted with 3,5-dimethylpiperidine by the method of Example 1 to form 2-fluoro-5-(3,5-dimethylpiperidinosulfonyl)benzoic acid. This product (0.0015 mole) is heated to 60° C. with diethylamine (10 ml.) and ethanol (3.0 ml.) to form a clear solution, and the reaction mixture is then heated at reflux temperature for 24 hours. The resulting brown solid is filtered off, dissolved in 1N NaOH, washed twice with ether, and the product precipitated by the addition of concentrated HCl. Recrystallization from diethyl ether replaced by isopropyl ether yields the product, m.p. 139.5°-140° C.

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