Abstract Treatment of perfluorinated benzocyclobutene, indan, and tetralin with SbF 5-SO 2 Cl 2, as well as of their 1, 1-dichloro analogs with SbF 5, gave 1- chloropolyfluorobenzocycloalken-1-yl cations whose structure was studied by 19 F and 13 C NMR and confirmed by their transformations into perfluorinated ketones upon hydrolysis. Dissolution of perfluorinated benzocyclobutene, indan, and tetralin in excess SbF5 ...