Rearrangement of the carbon skeletion of perfluorinated 1-isopropyl-, 1-methyl-1-isopropyl-, and 1-methyl-2-isopropylbenzocyclobutenes by the action of antimony pentafluoride

Abstract

Perfluorinated 1-isopropyl-, 1-methyl-1-isopropyl-, and 1-methyl-2-isopropylbenzocyclobutenes isomerize under the influence of antimony pentafluoride to perfluorinated alkylstyrenes and alkylindans. The process may be accompanied by dealkylation and also by fluorination and defluorination of the products. With antimony pentafluoride at 50°C perfluoro-1-methyl-1-isopropylbenzocyclobutene gives perfluoro-α,β,β,o-tetramethylstyrene, which isomerizes under the influence of antimony pentafluoride at 130°C into perfluoro-1,2,2-trimethylindan, and the latter forms perfluoro-2,3-dimethylindene under the reaction conditions. Perfluoro-1-methyl-2-isopropylbenzocyclobutene is not changed in the presence of antimony pentafluoride at 50°C but isomerizes to perfluoro-1-isopropylindan at 90°C. The latter is transformed under these conditions into the above-mentioned tetramethylstyrene. Perfluoro-1-isopropylbenzocyclobutene does not react with antimony pentafluoride at 130°C, but at 170°C it gives a mixture of perfluorinated 2,2-dimethylindan, 2,3-dimethylindene, 2,3-dimethyl-4,5,6,7-tetrahydroindene, and 2-isobutyltoluene, which is converted into perfluoro-o-xylene under the reaction conditions.