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

Abstract Heavy metal on Lewis acid : The combination of lanthanide metals and AlCl 3 has been employed for selective single C−F activation in benzofulvenes comprising an exocyclic CF 3 substituent. Intermediate ϵ,ϵ‐difluorinated metal‐dienyl species react with a large variety of aldehydes in a highly regio‐ and diastereoselective fashion to afford 1,1‐disubstituted indenes bearing a difluorovinyl group. These new building blocks have been further transformed through a hydrogenation–cyclization process into fluorinated heterocyclic spiro compounds.