Coplanar Atropochiral 5 <i>H</i> ‐Cyclopenta[2,1‐ <i>b</i> :3,4‐ <i>b</i> ′]dipyridine Ligands: Synthesis and Applications in Asymmetric Ring‐Opening Reaction
Han Yang, Xiaojie Sun, Zhen Chen, Chengming Jiang, Longhui Duan, Jinbo Zhao, Zhenhua Gu
Abstract
Bipyridines represent a class of ligands renowned for their versatility and efficacy in numerous transition metal-catalyzed reactions. Chiral bipyridine ligands are noted for their distinctive reactivity and stereoselectivity. In this work, we have designed and synthesized a class of bipyridine ligands endowed with an axially chiral scaffold. These ligands feature: (a) a precisely aligned coplanar bipyridine framework that is beneficial for metal chelation; (b) a spacious environment around the metal-bipyridine complexes, capable of hosting substrates with substantial steric bulk; (c) a chiral pocket induced by the axially chiral architecture. These atropochiral planar bipyridine ligands were successfully applied in copper-catalyzed ring-opening reactions of cyclic diaryliodoniums with bulky secondary amines, achieving high efficiency and stereoselectivity that were unsuccessful in our previous efforts.