Cobalt catalyzed practical hydroboration of terminal alkynes with time-dependent stereoselectivity.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 38467660.
- Also identified by DOI 10.1038/s41467-024-46550-y and PMC identifier 10928171.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
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<sup>-1</sup>) 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.