Carbonylation of Polyfluorinated Alkylbenzenes and Benzocycloalkenes at the Benzyl C-F and C-Cl Bonds Under the Action of CO/SbF₅

The carbonylation at the benzyl C-Hal bonds (Hal = F, Cl) of a number of polyfluorinated alkylbenzenes and benzocycloalkenes using carbon monoxide in the presence of SbF₅ is described. The reaction provided the corresponding α-arylcarboxylic acids or their methyl esters following aqueous or methanol treatment. The products of double carbonylation were obtained from bis(chloromethyl)tetrafluorobenzenes and benzal fluorides. For benzal chloride derivatives, the possibility of selective mono- or dicarbonylation was shown to depend on the amount of antimony pentafluoride. In the case of polyfluorinated secondary benzyl halides with a hydrogen atom at the α-carbon atom and vicinal fluorine atoms, the addition of CO was found to be accompanied by the elimination of HF, resulting in α,β-unsaturated α-arylcarboxylic acids. The double elimination of HF during the carbonylation of 1,4-dichloro-2,2,3,3,5,6,7,8-octafluorotetralin yielded dimethyl perfluoronaphthalene-1,4-dicarboxylate.