Synthesis of <i>gem</i>-Difluoromethylenated Polycyclic Cage Compounds

The synthesis of <i>gem</i>-difluoromethylenated polycyclic cage compounds, utilizing PhSCF₂SiMe₃ as a <i>gem</i>-difluoromethylene building block, is described. The fluoride-catalyzed nucleophilic addition of PhSCF₂SiMe₃ to both maleic anhydride–cyclopentadiene and maleic anhydride–cyclohexadiene adducts was accomplished with high stereoselectivity to provide the corresponding adducts that were treated with Grignard reagents, followed by acid-catalyzed lactonization to afford the corresponding γ-butyrolactones, each as a single isomer. These γ-butyrolactones underwent intramolecular radical cyclization to give the corresponding tetracyclic cage γ-butyrolactones, which were employed as precursors for the synthesis of <i>gem</i>-difluoromethylenated tetracyclic cage lactols or tetracyclic cage furans, upon treatment with Grignard reagents