Jankins Tanner C, Rubel Camille Z, Ho Hang Chi, Martin-Montero Raul, Engle Keary M
Department of Chemistry, The Scripps Research Institute 10550N. Torrey Pines Road, La Jolla CA 92037 USA
Chem Sci. 2024 Dec 4;16(5):2307-2315. doi: 10.1039/d4sc07093c. eCollection 2025 Jan 29.
Catalytic alkene isomerization is a powerful synthetic strategy for preparing valuable internal alkenes from simple feedstocks. The utility of olefin isomerization hinges on the ability to control both positional and stereoisomerism to access a single product among numerous potential isomers. Within base-metal catalysis, relatively little is known about how to modulate reactivity and selectivity with group 6 metal-catalyzed isomerization. Here, we describe a tungsten-catalyzed, positionally selective alkene isomerization reaction in which tuning the ligand environment grants access to either the - or -stereoisomer. The reactions employ simple, commercially available precatalysts and ligands. Preliminary mechanistic studies suggest that the ligand environment around 7-coordinate tungsten is crucial for stereoselectivity, and that substrate directivity prevents over-isomerization to the conjugated alkene. These features allow for exclusive formation of β,γ-unsaturated carbonyl compounds that are otherwise difficult to prepare.
催化烯烃异构化是一种从简单原料制备有价值的内烯烃的强大合成策略。烯烃异构化的实用性取决于控制位置异构和立体异构以在众多潜在异构体中获得单一产物的能力。在贱金属催化领域，对于如何通过第6族金属催化的异构化来调节反应性和选择性了解相对较少。在此，我们描述了一种钨催化的位置选择性烯烃异构化反应，其中通过调节配体环境可以得到α-或β-立体异构体。该反应使用简单的、市售的预催化剂和配体。初步机理研究表明，七配位钨周围的配体环境对立体选择性至关重要，并且底物的导向性可防止过度异构化为共轭烯烃。这些特性使得能够独家形成难以制备的β,γ-不饱和羰基化合物。
