Pd-Catalyzed Fluorocarbonylation of Iodoarenes with Difluoromethyl Benzoates

Palladium-catalyzed fluorocarbonylation of iodoarenes using difluoromethyl benzoate (DFBz) or difluoromethyl p-cyano-benzoate (DFBz-CN) as a fluorocarbonylation reagent has been developed, affording structurally diverse acyl fluorides as products. Both DFBz and DFBz-CN reagents are conveniently prepared through insertion of difluorocarbene into the O–H bonds of carboxylic acids. The activation of these two difluoromethyl benzoates with CsF generates formyl fluoride (HCOF), which readily decomposes into CO and HF. Therefore, both DFBz and DFBz-CN can be successfully used as safe surrogates of CO. This study provides not only a new synthetic method for fluorocarbonylation but also intriguing insights into the different reactivity between the previously known trifluoromethyl benzoate (TFBz, an effective CF₃O^–synthon) and the currently studied difluoromethyl benzoate (DFBz, not a satisfactory HCF₂O^–synthon).