Thomas Fabian, Oster Matthias, Schön Florian, Göbgen Kai C, Amarouch Benedikt, Steden Dominik, Hoffmann Alexander, Herres-Pawlis Sonja
Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1a, 52074 Aachen, Germany.
Dalton Trans. 2021 May 21;50(19):6444-6462. doi: 10.1039/d1dt00832c. Epub 2021 Apr 28.
Copper nitrene complexes are highly reactive species and are known as intermediates in the copper catalyzed C-H amination. In this study, three novel copper tosyl nitrene complexes were synthesized at low temperatures, stabilized with heteroscorpionate ligands of the bis(pyrazolyl)methane family. The copper nitrenes were obtained by the reaction of a copper(i) acetonitrile complex with PhINTs in dichloromethane. We show that the ligand design has a major influence on the catalytic activity and the thermal stability of the copper nitrene complex. Not only the choice of the third N donor, but also the substituent in the 5-position of the pyrazolyl moiety, have an impact on the stability. Furthermore, the novel copper nitrene complexes were used for catalytic aziridination of styrenes and C-H amination reactions of aromatic and aliphatic substrates under mild reaction conditions. Even challenging substrates like benzene and cyclohexane were aminated with good yields. The copper nitrene complexes were characterized using UV/Vis spectroscopy, low temperature Evans NMR spectroscopy, density functional theory, domain-based local pair natural orbital coupled cluster calculations (DLPNO-CCSD(T)) and cryo-UHR mass spectrometry.
铜氮宾配合物是高活性物种，在铜催化的C-H胺化反应中作为中间体为人所知。在本研究中，三种新型的对甲苯磺酰基铜氮宾配合物在低温下合成，并用双（吡唑基）甲烷家族的异蝎形配体进行稳定化。通过铜（I）乙腈配合物与二氯甲烷中的PhINTs反应得到铜氮宾。我们表明配体设计对铜氮宾配合物的催化活性和热稳定性有重大影响。不仅第三个氮供体的选择，而且吡唑基部分5-位的取代基都对稳定性有影响。此外，新型铜氮宾配合物用于在温和反应条件下催化苯乙烯的氮杂环丙烷化反应以及芳香族和脂肪族底物的C-H胺化反应。甚至像苯和环己烷这样具有挑战性的底物也能以良好的产率进行胺化。使用紫外/可见光谱、低温埃文斯核磁共振光谱、密度泛函理论、基于域的定域对自然轨道耦合簇计算（DLPNO-CCSD(T)）和低温超高分辨质谱对铜氮宾配合物进行了表征。
