Stereocontrol in Photochemical Reactions

Abstract: Photochemistry is intriguing as a synthetic tool because the absorption of light by an organic molecule results in the formation of exceptionally energetic reactive intermediates that can react in ways that are inaccessible to ground-state molecules. However, this high reactivity is also a challenge for stereoselective synthesis: control over the stereochemistry of photochemical reactions, particularly using enantioselective catalysts, has been a long-standing challenging synthetic problem with few general solutions. We recently developed a method for highly enantioselective [2+2] photocycloaddition reactions using a combination of chiral Lewis acid and transition metal photocatalysis. This dual catalyst approach offers a robust strategy to control the reactivity of a wide range of reactive intermediates that can easily be generated using photoredox catalysis.