This invention relates to 2-pentafluorosulfanylnapthalene, substituted derivatives thereof and to a process for producing naphthalene carrying an SF.sub.5 group. A 3-step process is employed wherein 1,4-dihydronaphthalene is reacted with pentafluorosulfanyl halide. Next the resulting 3-halo-2-pentafluorosulfanylnaphthalene or derivative is converted to 2-pentafluorosulfanyl-1,4-dihydronaphthalene or derivative by treatment with a base and subsequently transformed into pentafluorosulfanylnaphthalene by removing hydrogen atoms.