研究室工作進展 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.

三價銅化合物還原消除生成碳-碳鍵或者碳-雜原子鍵，被認為是銅催化或促進的有機合成反應中的關鍵步驟。雖然有文獻報道三價銅化合物的合成與分離，但是，其還原消除生成碳-碳鍵或者碳-雜原子鍵的反應研究幾乎沒有報道，因此三價銅化合物作為銅催化或促進的有機合成反應中的關鍵中間體的直接實驗證據不足。

本工作在該課題組雙锂試劑化學的基礎上，首次合成并結構确認了新穎的螺環三價銅及其相應的螺環一價銅化合物，發現這些不同價态的化合物之間可以發生定量的氧化還原轉化。更為重要的是，研究發現這些結構确認的三價銅化合物可以發生還原消除高效地生成碳-碳鍵，同時生成相應的一價銅物種。