Tailor-made well-defined copper nitrenes for catalytic asymmetric C-H amination and aziridination

硝烯是一种开壳式低价化合物，由于硝烯氮上的电子缺乏构型，这种化合物特别具有活性。例如，可以从适当的金属络合物和有机叠氮化合物或亚氨基碘烷中产生硝烯，由此金属被氧化，并且硝烯的价态被金属-氮键饱和。这类金属腈被认为是催化直接胺化和将氮转移到不饱和有机底物和杂原子上的关键物种。特别是，末端硝烯的出现被认为是所述反应的反应性的决定性因素。到目前为止，只有几个末端的硝酸铜得到了表征。通过特殊地操纵它们的电子性质，有可能增加金属硝烯的反应性，因此特殊的配体设计在这里是决定性的。通过X射线衍射、X-射线光电子能谱、电子自旋共振光谱、拉曼光谱和UV/Vis光谱研究了金属硝烯的价电子和成键比。此外，可以从理论上模拟电子性质以用于物种的识别，从而可以模拟光谱性质。到目前为止，在丁二烯催化反应中，主要起作用的是过渡金属(铜、钯、铁、Ru、银、Ir、Rh、Co、Mn)；由于铜的利用率高、毒性低，所以铜优于许多过渡金属。最有效的铜催化剂需要苛刻的热条件。然而，由于金属叠氮化物和亚胺碘溶液的爆炸性，必须不惜一切代价避免加热，出于安全原因，永远不会在工业上应用。此外，尽管对金属氮烯的催化研究已经有很多年了，但功能氮烯体系和功能催化剂之间很少有一致之处。在以前的研究中，我们能够证明双(吡唑基)甲烷稳定的铜-氮配合物以单重态的形式存在，这对于胺化和氮杂环化的区域选择性和对映选择性是非常有利的。我们现在希望通过手性地改变双(吡唑基)甲烷并将这个复杂的家族扩展到恶唑啉来进一步发展这一概念。通过定制配体的可能性，再加上来自光谱表征和动力学以及催化研究的反馈，可以有针对性地设计具有可调性能的活性金属-硝烯。此外，还将开发新的氮气源。一个重要的焦点也是各个自旋态与观察到的反应性之间的潜在关联。

Nitrenes are open-shell, low valent compounds, which are particularly reactive due to the electron deficiency configuration at the nitrene nitrogen. Nitrenes can be produced, for example, from suitable metal complexes and organic azides or iminoiodinanes, whereby the metal is oxidised and the valency of the nitrene is saturated by metal-nitrene bonds. Such metallonitrenes are considered key species for catalytic direct amination and nitrene transfer to unsaturated organic substrates and heteroatoms. In particular, the occurrence of terminal nitrenes is considered a decisive factor for the reactivity of the reactions addressed. So far, only a few terminal copper nitrenes have been characterised. By specifically manipulating their electronic properties, it is possible to increase the reactivity of metal nitrenes, whereby the special ligand design is decisive here. The valence electrons and bonding ratios of the metal nitrenes are experimentally accessible via XRD, XAS, ESR, Raman and UV/Vis spectroscopic investigations. In addition, the electronic properties can be modelled theoretically for the identification of the species and thus the spectroscopic properties can be simulated. In nitrene-mediated catalysis, mainly transition metals (Cu, Pd, Fe, Ru, Ag, Ir, Rh, Co, Mn) have played a role so far; due to the large availability and low toxicity, copper is superior to many transition metals. The most effective copper catalysts require harsh thermal conditions. However, the heating of metal-containing azide and iminoiodinane solutions must be avoided at all costs due to their explosive nature and will never find industrial application for safety reasons. Furthermore, although there have been catalytic studies on metal nitrenes for many years, there is rarely a congruence between a functional nitrene system and functional catalyst. In previous studies, we were able to show that bis(pyrazolyl)methane-stabilised copper-nitrene complexes exist as singlet, which is very advantageous for the regio- and enantioselectivity of aminations and aziridinations. We now want to develop this concept further by chirally varying the bis(pyrazolyl)methanes and also extending this complex family towards oxazolines. The possibility to tailor the ligands, together with feedback from spectroscopic characterisation and kinetic as well as catalytic studies, allows a targeted design of reactive metal-nitrenes with tunable properties. In addition, new nitrene sources are to be developed. An important focus is also the potential correlation of the respective spin states with the observed reactivity.