Expansion of the pentafluorobenzene ring and other skeletal transformations in the reaction of perfluoro(1,2-diethyl-1-phenyl-1,2-dihydrocyclobutabenzene) with antimony pentafluoride

The reaction of perfluoro(1-phenyl-1,2-diethyl-1,2-dihydrocuclobutabenzene) with SbF5 at 20°C, followed by treatment of the reaction mixture with water gave perfluoro {4-1-(2-propylphenyl)propylidene]-2,5-cyclohexadien-1-one} together with perfluoro4b,10-diethylbenzoa]azulen-7(4bH)-one] resulting from unusual expansion of the pentafluorobenzene ring to seven-membered ring. Analogous reaction at 90°C, apart from the above compounds, afforded perfluorinated 10-ethyl- and 3,10-diethylbenzoa]azulen-6(10H)-ones via elimination of C₂F₅ group from the seven-membered ring or its migration to the benzene ring.