Stereoselective Rhodium-Catalyzed Isomerization of Stereoisomeric Mixtures of Arylalkenes
Hongxuan Yang, Wenke Dong, Wencan Wang, Tao Li, Wanxiang Zhao*
*State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, Hunan 410082, P. R. China,
Email: zhaowanxianghnu.edu.cn
H. Yang, W. Dong, W. Wang, T. Li, W. Zhao, Synthesis, 2020, 52, 2833-2840.
DOI: 10.1055/s-0040-1707166
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Abstract
A rhodium complex catalyzes the synthesis of E-alkenes from E/Z mixtures of alkenes in the presence of B2pin2 under mild reaction conditions. The reaction offers broad functional group tolerance and has great application potential.
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Details
The document describes a new method for the stereoselective isomerization of E/Z mixtures of arylalkenes to produce high ratios of E-alkenes using a rhodium catalyst. The reaction employs B2pin2 and [Rh(cod)Cl]2 with Xantphos as the ligand in DME solvent at 60°C for 8 hours. This method offers mild reaction conditions, broad functional group tolerance, and high yields (86-91%) with excellent E/Z selectivity (>10:1). The study highlights the optimization of reaction conditions, including the amount of B2pin2 and the choice of ligands and solvents. The method was tested on various arylalkenes, demonstrating good compatibility with different functional groups and aromatic rings. Mechanistic studies suggest that the Rh-H species generated via dehydrogenative borylation is the active catalyst for the isomerization. The method was also applied to synthesize a resveratrol derivative, showcasing its potential for synthesizing functionalized molecules. The research was supported by the National Natural Science Foundation of China and other funding sources. The findings contribute to the development of reliable, mild, and neutral protocols for generating alkenes with excellent stereoselectivity, addressing limitations of conventional methods that often suffer from poor stereoselectivity and harsh conditions.
Key Words
isomerization, stereoselectivity, rhodium, alkenes, interconversion
ID: J66-Y2020