Dong Boliang, Peng Haihui, Motika Stephen E, Shi Xiaodong
Department of Chemistry, University of South Florida, Tampa, FL, 33620, USA.
Chemistry. 2017 Aug 16;23(46):11093-11099. doi: 10.1002/chem.201701970. Epub 2017 Jul 24.
The discovery of photoassisted diazonium activation toward gold(I) oxidation greatly extended the scope of gold redox catalysis by avoiding the use of a strong oxidant. Some practical issues that limit the application of this new type of chemistry are the relative low efficiency (long reaction time and low conversion) and the strict reaction condition control that is necessary (degassing and inert reaction environment). Herein, an alternative photofree condition has been developed through Lewis base induced diazonium activation. With this method, an unreactive Au catalyst was used in combination with Na CO and diazonium salts to produce a Au intermediate. The efficient activation of various substrates, including alkyne, alkene and allene was achieved, followed by rapid Au reductive elimination, which yielded the C-C coupling products with good to excellent yields. Relative to the previously reported photoactivation method, our approach offered greater efficiency and versatility through faster reaction rates and broader reaction scope. Challenging substrates such as electron rich/neutral allenes, which could not be activated under the photoinitiation conditions (<5 % yield), could be activated to subsequently yield the desired coupling products in good to excellent yield.
光辅助重氮盐对金（I）的氧化作用的发现，通过避免使用强氧化剂，极大地扩展了金氧化还原催化的范围。限制这种新型化学应用的一些实际问题是相对较低的效率（反应时间长和转化率低）以及必要的严格反应条件控制（除气和惰性反应环境）。在此，通过路易斯碱诱导的重氮盐活化开发了一种替代的无光条件。使用这种方法，将一种无活性的金催化剂与碳酸钠和重氮盐结合使用，以生成金中间体。实现了对包括炔烃、烯烃和丙二烯在内的各种底物的高效活化，随后快速进行金的还原消除，从而以良好至优异的产率得到碳-碳偶联产物。相对于先前报道的光活化方法，我们的方法通过更快的反应速率和更广泛的反应范围提供了更高的效率和通用性。具有挑战性的底物，如富电子/中性丙二烯，在光引发条件下无法被活化（产率<5%），但可以被活化，随后以良好至优异的产率得到所需的偶联产物。
