Lehnherr Dan, Ji Yining, Neel Andrew J, Cohen Ryan D, Brunskill Andrew P J, Yang Junyu, Reibarkh Mikhail
Process Research & Development , Merck & Co., Inc. , Rahway , New Jersey 07065 , United States.
J Am Chem Soc. 2018 Oct 24;140(42):13843-13853. doi: 10.1021/jacs.8b08596. Epub 2018 Oct 10.
We report the use of LED-NMR spectroscopy to study the reaction mechanism of a newly discovered photoinduced iron-catalyzed cycloisomerization of alkynols to cyclic enol ethers. By understanding on/off ligand binding to the catalyst, we were able to appropriately design reaction conditions to balance catalyst activity and stability. LED-NMR was demonstrated to be a powerful tool in elucidating reaction mechanisms of photochemical reactions. Temporal NMR spectroscopic data under visible light illumination (1) revealed the pre-catalyst activation mechanism, (2) proved that photon flux provides a unique external control of the equilibrium distribution between the pre-catalyst and active catalyst, and ultimately the rate of reaction, (3) provided information about the reaction driving forces and the turnover-limiting step, and (4) enabled both real-time structural and kinetic insights into elusive species (e.g., dissolved gases).
我们报道了利用发光二极管核磁共振光谱法（LED-NMR）来研究一种新发现的光诱导铁催化炔醇环异构化为环状烯醇醚的反应机理。通过了解配体与催化剂的结合与解离情况，我们能够合理设计反应条件，以平衡催化剂的活性和稳定性。结果表明，LED-NMR是阐明光化学反应机理的有力工具。可见光照射下的时间分辨核磁共振光谱数据：（1）揭示了前催化剂的活化机制；（2）证明了光子通量可对前催化剂与活性催化剂之间的平衡分布提供独特的外部控制，进而最终控制反应速率；（3）提供了有关反应驱动力和限速步骤的信息；（４）能够对难以捉摸的物种（如溶解气体）进行实时结构和动力学分析。
