Visible light photocatalysis - from racemic to asymmetric activation strategies.

In the last years, an increasing interest towards the development of novel enantioselective strategies in photocatalysis has been observed within the research community. The high challenge associated with the intrinsic nature of photochemical reactions has obstructed the rapid development of this research field in comparison with asymmetric thermal processes. However, recently, many outstanding enantioselective transformations have been achieved through mechanistically different approaches. Here, we disclose the most significant contributions, with a special emphasis on the various activation strategies. An introduction to photocatalysis and to the different activation modes is provided, followed by an historical perspective and landmark examples of their application in asymmetric reactions.