Photoreductive Deuteration of C=N Bonds by Au/CdS Nanosheets

α-Deuterated amines play crucial roles in preparation of deuterated active pharmaceutical ingredients for drug research-and-development (R&D), which requires the development of low-cost, site-selective, and efficient methodologies for their synthesis. D₂O is the most ideal and low-cost D-source but generally serves as a “proton pool” to react with the in situ generated carbanion from C=N bonds in prevalent methods that suffer from the poor substrate versatility. Herein, we report a photocatalytic water splitting (PWS) technology for the reductive deuteration of C=N bonds by Au/CdS nanocatalysts. Mechanism insights suggest that incorporating Au nanocatalysts onto CdS semiconductors is important in overcoming the intrinsic poor-photostability of the CdS semiconductor via sulfur fixation and enhancing the photocatalytic performance by improving the separation and migration efficiency of charge carriers. As a result, this PWS-based reductive deuteration strategy using reusable and robust photocatalysts and D₂O offers many advantages including mild conditions, site-selectivity, and good substrate versatility in the production of numerous valuable α-deuterated amines, including many deuterated bioactive molecules such as butenafine and enterovirus 71 inhibitors. © 2025 American Chemical Society.