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 1 N NaOH, washed twice with water, 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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