The obvious approach to the synthesis of 1 and its derivatives is by the (4 + 2)cyclo-addition of 5,5-difluorocyclopentadiene (3) to olefins Unfortunately, compound 3 is not known. However the tetrachloro derivative 4 is easily available and its cyclo-addition affords a route to the desired derivatives of 1 provided that the chlorineatoms can he removed without disturbing the fluorines. By extension of a wellestablished procedure some chlorinated 7,7-difluoronorbornenes were preparedas candidates for trial experiments of selective reduction.