Hydrogen‐Bonding Organocatalysis Enabled Photocatalytic Intramolecular [2+2]‐Cycloaddition Reaction

Abstract

The combination of organocatalytic activation and photocatalysis for enabling the intramolecular [2+2]‐cycloaddition of enones‐ene substrates bearing one Lewis base binding‐site is reported. While in a variety of solvents a poor conversion or no reaction takes place in the absence of a hydrogen bonding catalyst, the corresponding ring‐fused cyclobutane products could be built in moderate to good yields using a synergistic dual iridium‐urea co‐catalytic system. Control and mechanistic studies supported the postulated interaction between the organocatalyst and the substrate, which proved essential for an efficient energy transfer from the photosensitizer.