Generation of perfluoro- and 1-chloropolyfluorobenzocycloalken-1-yl cations and their relative stability

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 generated perfluorobenzocycloalken-1-yl cations in equilibrium with their precursors. The relative stability of perfluoro- and 1-chloropolyfluorobenzocycloalken-1-yl cations decreases as the size of the alicyclic fragment increases.