Preparation of benzoyl fluorides and benzoic acids from phenols via a dearomatization-rearomatization strategy

We describe here a method to generate both benzoyl fluorides and benzoic acids using 2,5-cyclohexadienones prepared from phenols via oxidative dearomatization. 2,5-Cyclohexadienones react with difluoromethyl 2-pyridyl sulfone under basic conditions to give gem-difluoroolefins in situ, which could be attacked by nucleophiles and further aromatized to form benzoyl fluorides. By changing the reaction conditions, benzoic acids could be formed efficiently in a one-pot fashion as well. The mild conditions and broad substrate scope make this transformation a unique approach for formal deoxyacylation of phenols without transition metal catalysis.