Key Laboratory of Green Chemistry & Technology, Ministry of Education, College of Chemistry, Sichuan University, 610064, Chengdu, China.
Shenzhen Grubbs Institute and Department of Chemistry, Southern University of Science and Technology, 518055, Shenzhen, China.
Nat Commun. 2023 Feb 22;14(1):990. doi: 10.1038/s41467-023-36677-9.
The hydrogenation of alkynes allows the synthesis of olefins, which are important feedstock for the materials, pharmaceutical, and petrochemical industry. Thus, methods that enable this transformation via low-cost metal catalysis are desirable. However, achieving stereochemical control in this reaction is a long-standing challenge. Here, we report on the chromium-catalyzed E- and Z-selective olefin synthesis via hydrogenation of alkynes, controlled by two carbene ligands. A cyclic (alkyl)(amino)carbene ligand that contains a phosphino anchor enables the hydrogenation of alkynes in a trans-addition manner, selectively forming E-olefins. With an imino anchor-incorporated carbene ligand, the stereoselectivity can be switched, giving mainly Z-isomers. This ligand-enabled geometrical stereoinversion strategy by one metal catalysis overrides common methods in control of the E- and Z-selectivity with two different metal catalysis, allowing for highly efficient and on-demand access to both E- and Z-olefins in a stereo-complementary fashion. Mechanistic studies indicate that the different steric effect between these two carbene ligands may mainly dominate the selective forming E- or Z-olefins in control of the stereochemistry.
炔烃的氢化允许烯烃的合成，烯烃是材料、制药和石化工业的重要原料。因此，通过低成本金属催化实现这种转化的方法是理想的。然而，在该反应中实现立体化学控制是一个长期存在的挑战。在这里，我们报告了通过铬催化的炔烃氢化反应，通过两个卡宾配体控制，实现 E-和 Z-选择性烯烃的合成。一种含有膦锚的环状（烷基）（氨基）卡宾配体能够以反式加成的方式进行炔烃的氢化，选择性地形成 E-烯烃。而带有亚氨基锚的卡宾配体则可以切换立体选择性，主要生成 Z-异构体。这种配体实现的几何立体反转策略通过一种金属催化来实现，克服了使用两种不同金属催化来控制 E-和 Z-选择性的常见方法，允许以立体互补的方式高效且按需获得 E-和 Z-烯烃。机理研究表明，这两种卡宾配体之间的不同空间效应可能主要控制立体化学中 E-或 Z-烯烃的选择性形成。
