Fokin Igor, Siewert Inke
Institut für Anorganische Chemie, Universität Göttingen, Tammannstr. 4, 37077, Göttingen, Germany.
Chemistry. 2020 Nov 6;26(62):14137-14143. doi: 10.1002/chem.202002075. Epub 2020 Oct 4.
Hydrogenation reactions are fundamental functional group transformations in chemical synthesis. Here, we introduce an electrochemical method for the hydrogenation of ketones and aldehydes by in situ formation of a Mn-H species. We utilise protons and electric current as surrogate for H and a base-metal complex to form selectively the alcohols. The method is chemoselective for the hydrogenation of C=O bonds over C=C bonds. Mechanistic studies revealed initial 3 e reduction of the catalyst forming the steady state species [Mn (H L)(CO) ] . Subsequently, we assume protonation, reduction and internal proton shift forming the hydride species. Finally, the transfer of the hydride and a proton to the ketone yields the alcohol and the steady state species is regenerated via reduction. The interplay of two manganese centres and the internal proton relay represent the key features for ketone and aldehyde reduction as the respective mononuclear complex and the complex without the proton relay are barely active.
氢化反应是化学合成中基本的官能团转化反应。在此，我们介绍一种通过原位形成Mn-H物种对酮和醛进行氢化的电化学方法。我们利用质子和电流作为H的替代物以及一种贱金属配合物来选择性地形成醇。该方法对C=O键的氢化比对C=C键具有化学选择性。机理研究表明，催化剂最初发生3e还原形成稳态物种[Mn (H L)(CO) ] 。随后，我们假定发生质子化、还原和内部质子转移形成氢化物物种。最后，氢化物和一个质子转移到酮上生成醇，并且稳态物种通过还原得以再生。两个锰中心的相互作用和内部质子传递是酮和醛还原的关键特征，因为相应的单核配合物以及没有质子传递的配合物几乎没有活性。
