TiO₂ Photocatalytic cyclization reactions for the syntheses of aryltetralones

This work focuses on a new strategy to overcome the overoxidation in heterogeneous TiO₂ photocatalysis and to realize high-efficiency photosynthesis. We demonstrate that TiO₂ photocatalysis can integrate C.C and C-LO formation in a tandem manner to achieve efficient oxidative cyclization for the syntheses of aryltetralones. This protocol does not need any additive besides the inexpensive and/or recyclable TiO₂, O₂, and (solar) light. High yields with excellent diastereoselectivities are obtained for a wide scope of electron-rich substrates. Our findings demonstrate that in contrast to the conventional overoxidation, as long as the radical cations possess sufficient reactivity toward nucleophilic addition, single-electron transfer processes in TiO₂ photocatalysis can be developed into a powerful tool to construct C.C bonds and even strained carbon rings.