Cu-catalyzed O-arylations of pyrazolin-5-ones using diaryliodonium salts

[Display omitted] A ligand and base-free copper-catalyzed method has been developed for the synthesis of O-arylated pyrazolin-5-ones from readily available reagents. This methodology can be applied to a broad substrate scope and exhibits tolerance towards a wide range of functional groups, including both electron-donating and -withdrawing groups. Moreover, the applicability of this protocol was further established by gram-scale synthesis. Additionally, control experiments demonstrated that the use of specific diaryliodonium salts, particularly those incorporating the 2,4,6-trimethoxyphenyl (TMP) auxiliary group, notably enhances reactivity in the O-arylation process of pyrazolin-5-ones.