Water and Air Stable Copper(I) Complexes of Tetracationic Catenane Ligands for Oxidative C−C Cross‐Coupling
Man Pang Tang, Lihui Zhu, Yulin Deng, Yi‐Xiang Shi, Samuel Kin‐Man Lai, Xiaoyong Mo, Xin‐Yu Pang, Chunyu Liu, Wei Jiang, Edmund C. M. Tse, Ho Yu Au‐Yeung
Abstract
Abstract Aqueous soluble and stable Cu(I) molecular catalysts featuring a catenane ligand composed of two dicationic, mutually repelling but mechanically interlocked macrocycles are reported. The ligand interlocking not only fine‐tunes the coordination sphere and kinetically stabilizes the Cu(I) against air oxidation and disproportionation, but also buries the hydrophobic portions of the ligands and prevents their dissociation which are necessary for their good water solubility and a sustained activity. These catenane Cu(I) complexes can catalyze the oxidative C−C coupling of indoles and tetrahydroisoquinolines in water, using H 2 O 2 as a green oxidant with a good substrate scope. The successful use of catenane ligands in exploiting aqueous Cu(I) catalysis thus highlights the many unexplored potential of mechanical bond as a design element for exploring transition metal catalysis under challenging conditions.