1,1-Difluoro- and 1,1-dichloro-1H-cyclopropa[a]naphthalenes (1a and 1b) are prepared via dehydrohalogenation of the appropriate brominated carbene adducts (2a and 2b, respectively) of 4-bromo-1,2-dihydronaphthalene. Upon dissolution of 1a in cold fluorosulfonic acid it furnishes the very short-lived cation 3; the latter is characterized by its 1H- and 19F-NMR spectra.
