| Abstract: | Evidence is produced to demonstrate that loss of CH2 from methanoannulenes is a multistep process initiated by a rearrangement yielding (at least in the case of 1,6-methano[10]annulene) the isomeric benzocycloheptenes. Loss of CF2, however, apparently is a cheletropic reaction accompanied by rearomatization, thus giving rise to the formation of the molecular ion of naphthalene in the case of 11,11-difluoro-1,6-methano[10]annulene. These findings present further evidence for the parallel behaviour of the bridged annulenes regarding thermal transformations and fragmentation of the molecular ions. |
