Cobalt-Catalyzed Migration Isomerization of Dienes
Jiajin Zhao, Guoxiong Xu, Xue Wang, Jiren Liu, Xiang Ren, Xin Hong* and Zhan Lu*
*Department of Chemistry, Zhejiang University, Hangzhou 310058, China,
Email: hxchem
zju.edu.cn, luzhanzju.edu.cn
J. Zhao, G. Xu, X. Wang, J. Liu, X. Ren, X. Hong, Z. Lu, Org. Lett., 2022, 24, 4592-4597.
DOI: 10.1021/acs.orglett.2c01701
see article for more reactions
Abstract
A cobalt-catalyzed multipositional isomerization of conjugated dienes is operationally simple and atom-economical using readily available starting materials with an E:Z mixture to access disubstituted 1,3-dienes with excellent yields and good E,E stereoselectivity. A mechanism via alkene insertion of cobalt hydride species and β-H elimination of a π-allyl cobalt intermediate is proposed.
see article for more examples
proposed mechanism
General Procedure for Isomerization of Conjugated Dienes:
A 25 mL Schlenk flask equipped with a magnetic stirrer and a flanging rubber plug was dried with flame. When cooled to ambient temperature, it was transferred into a glove box. Then Lg•CoCl2 complex (0.009 mmol, 3 mol%), NaBHEt3 (0.027 mmol, 9 mol%), dienes (0.3 mmol, 1.0 equiv), and THF (0.5 mL) were added sequentially. The mixture was stired at room temperature for 0.5-70 h. Then the resulting solution was removed out of the glove box and quenched with 10 mL of PE and filtered through a pad of silica gel, and washed with PE (or other suitable solvent) (3 x 10 mL). The combined filtrate was concentrated and the conversion was determined by 1H NMR of crude product using TMSPh as an internal standard. The residue was purified by flash column chromatography to give the corresponding product.
Key Words
ID: J54-Y2022
