Hidden Enantioselective Hydrogenation of N-Silyl Enamines and Silyl Enol Ethers in Net C=N and C=O Hydrosilylations Catalyzed by Ru-S Complexes with One Monodentate Chiral Phosphine Ligand
Hidden Enantioselective Hydrogenation of N-Silyl Enamines and Silyl Enol Ethers in Net C=N and C=O Hydrosilylations Catalyzed by Ru-S Complexes with One Monodentate Chiral Phosphine Ligand
复制标题
DOI：
10.1021/acs.organomet.7b00030
复制
发表时间：
2017-02-27
期刊：
影响因子：
2.8
通讯作者：
Oestreich, Martin
中科院分区：
文献类型：
--
作者：
Baehr, Susanne;Oestreich, Martin
硫酸钌配合物与单手性单齿膦配体应用于烯化胺和酮的对映选择性硅氢化反应。催化剂的结构特征排除了在对映体选择性测定步骤中钌中心存在多个膦配体。在这些还原反应中获得的对映体过量是适度的（高达66% ee），但立体化学结果使实验分析在这种催化中起作用的反应途径成为可能。由连续的N-Si/O -Si脱氢偶联和烯胺/烯醇醚加氢组成的两步序列是主要的作用机制。这两个步骤都涉及到配位不饱和钌配合物的Ru-S键的协同键激活：脱氢偶联中的Si-H键激活和氢化中的异裂解H-H分裂。先前记录的副反应，如去质子化/质子化平衡以及直接竞争的C=N或C=O氢化已被排除在外。
Ruthenium thiolate complexes with one chiral monodentate phosphine ligand are applied to enantioselective hydrosilylation of enolizable 'mines and ketones. The structural features of the catalyst exclude the presence of more than one phosphine ligand at the ruthenium center in the enantioselectivity-determining step. The enantiomeric excesses obtained in these reduction reactions ate moderate (up to 66% ee), but the stereochemical outcome enables an experimental analysis of the reaction pathways operative in this catalysis. A two-step sequence consisting of successive N-Si/O Si dehydrogenative coupling and enamine/enol ether hydrogenation is, the prevailing mechanisin Of action. Both steps involve cooperative bond activation at the Ru-S bond of the coordinatively unsaturated ruthenium complex: Si-H bond activation in the dehydrogenative coupling and heterolytic H-H splitting in the hydrogenation. Previously documented side reactions such as deprotonation/protonation equilibria as well as competing direct C=N or C=O hydrogenation have been excluded.