Wen Jinglan, Huang Yahao, Zhang Yu, Grützmacher Hansjörg, Hu Peng
Institute of Green Chemistry and Molecular Engineering, School of Chemistry, Sun Yat-sen University, Guangzhou, 510006, PR China.
Lehn Institute of Functional Materials, School of Chemistry, Sun Yat-sen University, Guangzhou, 510006, PR China.
Nat Commun. 2024 Mar 12;15(1):2208. doi: 10.1038/s41467-024-46550-y.
Stereodefined vinylboron compounds are important organic synthons. The synthesis of E-1-vinylboron compounds typically involves the addition of a B-H bond to terminal alkynes. The selective generation of the thermodynamically unfavorable Z-isomers remains challenging, necessitating improved methods. Here, such a proficient and cost-effective catalytic system is introduced, comprising a cobalt salt and a readily accessible air-stable CNC pincer ligand. This system enables the transformation of terminal alkynes, even in the presence of bulky substituents, with excellent Z-selectivity. High turnover numbers (>1,600) and turnover frequencies (>132,000 h) are achieved at room temperature, and the reaction can be scaled up to 30 mmol smoothly. Kinetic studies reveal a formal second-order dependence on cobalt concentration. Mechanistic investigations indicate that the alkynes exhibit a higher affinity for the catalyst than the alkene products, resulting in exceptional Z-selective performance. Furthermore, a rare time-dependent stereoselectivity is observed, allowing for quantitative conversion of Z-vinylboronate esters to the E-isomers.
立体定向乙烯基硼化合物是重要的有机合成子。E-1-乙烯基硼化合物的合成通常涉及将B-H键加成到末端炔烃上。选择性生成热力学上不利的Z-异构体仍然具有挑战性，因此需要改进方法。在此，引入了一种高效且经济高效的催化体系，该体系由钴盐和易于获得的空气稳定的CNC钳形配体组成。该体系能够实现末端炔烃的转化，即使存在庞大的取代基，也具有出色的Z-选择性。在室温下实现了高周转数（>1600）和高周转频率（>132000 h⁻¹），并且该反应可以顺利放大至30 mmol。动力学研究表明对钴浓度呈形式上的二级依赖性。机理研究表明，炔烃对催化剂的亲和力高于烯烃产物，从而导致了出色的Z-选择性性能。此外，观察到一种罕见的时间依赖性立体选择性，使得Z-乙烯基硼酸酯能够定量转化为E-异构体。
