Research news, Oct. 26th, 2017

Reductive elimination of Cu(III) intermediates is often proposed as a key step in many copper-catalyzed or -mediated C?C or C?heteroatom bond-forming reactions. However, there still lacks concrete evidence on this key step, mainly because Cu(III) complexes are usually too unstable to be isolated and structurally characterized. 

In this work, we report the synthesis, structural characterization, redox transformation and reductive elimination of spiro organocopper(III) complexes. 

This work has the following features: 

(1) Synthesis and Structural Characterization of Spiro Organocopper(III) and Organocopper(I) complexes: Spiro organocopper(III) complexes and their analogous spiro organocopper(I) complexes were synthesized and structurally characterized for the first time;

(2) Redox Transformation between the spiro Cu(I) and Cu(III) Complexes:  A quantitative redox transformation between the spiro organocopper(III) and organocopper(I) complexes was experimentally observed by treating with reductants or oxidants, respectively;

(3) Concrete Evidence of Reductive Elimination of Organocopper(III) complexes: The structurally well-defined spiro organocopper(III) complexes were determined to undergo reductive elimination to form C?C bonds, along with generation of their corresponding Cu(I) species.