Visible-light-driven enantioselective protonation: a new Frontier in asymmetric catalysis.

Enantioselective protonation represents a direct and effective method for constructing tertiary carbon stereocenters, which are prevalent in natural products and bioactive compounds. However, achieving catalytic asymmetric protonation has long posed challenges due to difficulties in controlling stereoselectivity. The small size of protons and their rapid transfer rates complicate the selective delivery to active intermediates, resulting in convoluted reaction pathways and pronounced background reactions. In recent years, light-driven photocatalysis has emerged as a powerful strategy in asymmetric protonation reactions, significantly broadening the range of reaction pathways and substrate types. In this review, we highlight recent advancements in this area, focusing on photoinduced single-electron transfer and energy transfer processes, where photosensitizers generate reactive intermediates for asymmetric protonation. This approach not only expands the scope of asymmetric catalysis but also presents new opportunities for green and sustainable chemistry, effectively addressing critical challenges in the construction of complex molecules.