Palladium‐Catalyzed Directed Atroposelective C−H Iodination to Synthesize Axial Chiral Biaryl N‐Oxides via Enantioselective Desymmetrization Strategy
Linxi Yao, Alemayehu Gashaw Woldegiorgis, Shaoying Huang, Yongtao Wang, Xufeng Lin
Abstract
The discovery of enantioselective desymmetrization reactions to provide practical synthesis of enantio-enriched atropisomeric biaryls is a challenging topic in the field of asymmetric catalysis. Herein, we report a highly enantioselective desymmetrization reaction for the synthesis of axially chiral biaryl N-oxides by atroposelective C-H iodination by using Pd(II) coordinated by N-benzoyl-l-phenylalanine as a chiral catalyst at room temperature. A broad range of products were obtained in high yields (up to 99 %) with excellent enantioselectivities (up to 98 % ee). The products could be synthesized in gram scale, one of which was proved to be a powerful organocatalyst in asymmetric allylation reaction. Mechanistic evidence as well as DFT calculations point towards the factors that lead to high reactivity and excellent enantiocontrol in this reaction.