Photocatalytic intermolecular dearomative cycloaddition of phenanthrenes and naphthalenes with excited gem-difluoroalkenes

Dearomative cycloaddition is a crucial method for constructing three-dimensional (3D) complex molecules from simple precursors, but the difficulty in exciting many arenes limits the application of this method. Herein, we report a photocatalytic intermolecular dearomative [2 + 2]/[4 + 2] cycloaddition of phenanthrenes and naphthalenes with excited gem-difluoroalkenes for the synthesis of fused gem-difluorocyclobutanes and gem-difluorocyclohexanes. Previous dearomative cycloaddition reactions involving excited phenanthrenes and naphthalenes required electron-deficient substituents to lower their excited-state energies, allowing for energy-transfer catalysis to occur. Our strategy involves excited-state gem-difluoroalkenes undergoing dearomative cycloaddition reactions with ground-state phenanthrenes and naphthalenes, enabling it to tolerate not only electron-deficient arenes but also electron-neutral and electron-rich arenes.