Sensitized photochemistry evolved over the last 20 years into an enabling technology for the synthesis of complex organic molecules due to new mechanistic concepts and advances in light sources. The use of visible light and dual catalytic systems allow new transformations and improves existing protocols in selectivity or reaction conditions. Visible light is an ideal reagent for chemistry: It is cheap, safe and can be used in large excess, but there are still challenges: Compared to chemical bond energies, the energy of a visible light photon is small and photocatalytic activation of stronger bonds therefore requires special strategies. Photoinduced electron transfer induces typically radical reactions, but ionic transformations would be equally desirable. Can organic dyes and heterogeneous semiconductors serve as efficient and sustainable alternatives to metal complex photocatalysts?
We discuss opportunities using visible light in organic synthesis and approaches to overcome current challenges.
Burkhard König received his Ph.D. in 1991 from the University of Hamburg. He continued his scientific education as a post-doctoral fellow with Prof. M. A. Bennett, Research School of Chemistry, Australian National University, Canberra, and Prof. B. M. Trost, Stanford University. Since 2000, he is a full professor of organic chemistry at the University of Regensburg. His current research interests revolve around the use of photoredox catalysis in organic synthesis.