Copper catalysis with redox-active ligands.

Agnideep Das,Marine Desage-El Murr,Cheriehan Hessin,Yufeng Ren

doi:10.3762/bjoc.16.77

Abstract

Copper catalysis finds applications in various synthetic fields by utilizing the ability of copper to sustain mono- and bielectronic elementary steps. Further to the development of well-defined copper complexes with classical ligands such as phosphines and N-heterocyclic carbenes, a new and fast-expanding area of research is exploring the possibility of a complementing metal-centered reactivity with electronic participation by the coordination sphere. To achieve this electronic flexibility, redox-active ligands can be used to engage in a fruitful “electronic dialogue” with the metal center, and provide additional venues for electron transfer. This review aims to present the latest results in the area of copper-based cooperative catalysis with redox-active ligands.

Highlights

Interaction of earth-abundant metals, such as copper, with radical ligands is originally known from biological systems such as metalloenzymes [1]
This review aims to present the latest results in the area of copper-based cooperative catalysis with redox-active ligands
The unique electronic interaction due to matching or inverted energy levels between metal and ligand leads to valence tautomerism [5,6,7,8], which paves the way for orchestrated electronic events occurring within the metal complex and influences the chemical reactivity of the complex

Summary

Introduction

Interaction of earth-abundant metals, such as copper, with radical ligands is originally known from biological systems such as metalloenzymes [1]. Among the myriad of existing enzymes, galactose oxidase (GAO) is a copper-based enzyme performing the two-electron oxidation of galactose through a mechanism involving the metal and a neighboring tyrosine radical ligand for the shuttling of overall two protons and two electrons. This peculiar mechanism is enabled by transient storage of electronic density on the tyrosine ligands and perfectly illustrates the central role of ancillary pro-radical ligands in biological systems. While the field of catalysis with redox-active ligands is itself a much broader area, we shall limit our discussion to copper catalysis with redox-active ligands and the present review aims at provid-

Objectives

Conclusion