Carbon Dioxide → 5-Fluoro-2,2-dimethyl-2H-1,3-benzodioxole-4-carboxylic acid

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Reaction Steps

In a flask were placed 29.3 g (0.174 mole) of 2,2-dimethyl-5-fluoro-1,3-benzodioxole and 200 mL of dry tetrahydrofuran, and the resulting solution was cooled to -78° C. To this solution was added dropwise 66.4 mL (0.166 mole) of a 2.5 M solution of n-butyllithium in hexanes. This mixture was stirred at -78° C. for one hour after which a carbon dioxide atmosphere was placed above the reaction mixture. The temperature was allowed to warm to ambient conditions during a 16 hour period while maintaining the carbon dioxide atmosphere. At the conclusion of this period the solvent was evaporated under reduced pressure, and diethyl ether was added to the residue. This mixture was extracted with water, and the water extract was in turn extracted with diethyl ether. The aqueous phase was separated and acidified with hydrochloric acid. The acidified mixture was then extracted with methylene chloride. The methylene chloride extract was washed with water, dried over anhydrous magnesium sulfate, and filtered. The filtrate was evaporated under reduced pressure, leaving 19 g of 2,2-dimethyl-5-fluoro-1,3-benzodioxol-4-ylcarboxylic acid as the residue. The NMR spectrum was consistent with the proposed structure.

Provenance & Evidence