Highly Regioselective Cobalt‐Catalyzed Hydroboration of Internal Alkynes

• Published in: Angewandte Chemie 2022-09, Vol.134 (36), p.n/a
• Main Authors: Zhang, Yan‐Dong, Li, Xiao‐Yu, Mo, Qian‐Kun, Shi, Wen‐Bin, Zhao, Jia‐Bao, Zhu, Shou‐Fei
• Format: Article
• Language: English
• Subjects: Alkenes; Alkenylborates; Alkynes; Catalysts; Chemical reactions; Chemistry; Cobalt; Cobalt Catalysis; Cyclopropane; Diphosphine Ligands; Hydroboration; Internal Alkynes; Ligands; Organic chemistry; Regioselectivity; Rigid structures; Selectivity; Stereoselectivity
• ISSN: 0044-8249; 1521-3757
• DOI: 10.1002/ange.202208473

Herein, we report the development of new Co complexes that have cyclopropane‐based diphosphine ligands and can catalyze highly chemo‐, regio‐, and stereoselective hydroboration reactions of unsymmetrical internal alkynes. These reactions exhibited unusual regioselectivity: specifically, reactions of aryl alkyl internal alkynes showed excellent cis‐β‐addition selectivity, and reactions of dialkyl internal alkynes gave excellent cis‐α‐addition selectivity. Highly regioselective hydroboration of unsymmetrical dialkyl internal alkynes cannot be achieved by other known methods. The reactions described herein are highly synthetically useful, particularly for the stereoselective synthesis of trisubstituted alkenylborates and alkenes. Mechanistic studies indicate that a CoI−H species is a plausible active catalyst and the rigid structure of the cyclopropane skeleton of the ligands and the crowded reaction pocket were responsible for the unprecedented regioselectivity. A highly selective hydroboration of unsymmetrical internal alkynes featuring unique regioselectivity, broad substrate scope and good functional group compatibility was realized by using cobalt catalysts modified with newly developed cyclopropane‐based diphosphine ligands. The current protocol enabled the synthesis of novel alkenyl borates and improved the synthetic efficiency of bioactive compounds.