研究室工作进展 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.

三价铜化合物还原消除生成碳-碳键或者碳-杂原子键，被认为是铜催化或促进的有机合成反应中的关键步骤。虽然有文献报道三价铜化合物的合成与分离，但是，其还原消除生成碳-碳键或者碳-杂原子键的反应研究几乎没有报道，因此三价铜化合物作为铜催化或促进的有机合成反应中的关键中间体的直接实验证据不足。

本工作在该课题组双锂试剂化学的基础上，首次合成并结构确认了新颖的螺环三价铜及其相应的螺环一价铜化合物，发现这些不同价态的化合物之间可以发生定量的氧化还原转化。更为重要的是，研究发现这些结构确认的三价铜化合物可以发生还原消除高效地生成碳-碳键，同时生成相应的一价铜物种。