Cu(II)-Catalyzed H/D exchange of indole derivatives

Cu(OTf)2 was explored as an efficient catalyst for hydrogen deuterium (H/D) exchange of indole derivatives. The advantage of this reaction is that deuteration selectivity can be adjusted by changing reaction parameters. When the reaction was performed with 10 mol% of Cu(OTf)2 as a catalyst in dioxane at 80 °C, deuteration preferentially occurred at C3 position of indole with high atom% deuterium incorporation. Furthermore, per-deuterated indole derivatives could be achieved by performing the reaction with higher catalyst loading in toluene at 120 °C. Performing the reaction on a continuous flow reactor facilitates the scale-up process, affording deuterated products with a throughput of 3.9 g/h.