Deoxyfluorination of Carboxylic Acids via an Generated Trifluoromethoxide Salt.

An generated pyridinium trifluoromethoxide salt (PyOCF) is a highly effective deoxyfluorination reagent for the synthesis of acid fluorides. PyOCF is formed at room temperature from the reaction of 2,4-dinitro(trifluoromethoxy)benzene with 4-dimethylaminopyridine. PyOCF undergoes slow release of fluorophosgene and fluoride, which serve as the electrophile and nucleophile, respectively, for deoxyfluorination. A wide substrate scope and high functional group tolerance are demonstrated. Furthermore, the acid fluorides can be purified by filtration and telescoped to various known reactions.