Generation of ϵ,ϵ‐Difluorinated Metal‐Pentadienyl Species through Lanthanide‐Mediated C−F Activation

The combination of lanthanide metals and AlCl3 has been employed for the selective single C-F activation in benzofulvenes having an exocyclic CF3-substituent. The intermediately formed e,e-difluorinated metal-dienyl species react with a large variety of aldehydes in a highly regio and diastereoselective fashion to afford 1,1-disubstituted indenes carrying a difluorovinyl group. These new building blocks have been further transformed through a hydrogenation-cyclisation process into fluorinated heterocyclic spiro compounds.