Copper(I)/Copper(II)-Assisted Tandem Catalysis: The Case Study of Ullmann/Chan-Evans-Lam N1,N3-Diarylation of 3-Aminopyrazole

Abstract Unprecedented Cu I /Cu II ‐assisted tandem catalysis allowing an Ullmann/Chan–Evans–Lam sequence was achieved. This three‐component, one‐pot reaction triggered by a change in the oxidation state of the metal leads to the selective N 1 ,N 3 ‐diarylation of 3‐aminopyrazole. This new method should be a valuable tool for small‐molecule drug discovery that requires suitable regio‐ and/or chemoselective strategies for the N‐arylation of nitrogen‐containing heterocycles.