Design and Synthesis of Planar-Chiral Oxazole–Pyridine <i>N</i>,<i>N</i>-Ligands: Application in Palladium-Catalyzed Asymmetric Acetoxylative Cyclization
Yu-Qing Bai, Xinwei Wang, Bo Wu, Xiaoqing Wang, Rong‐Zhen Liao, Man Li, Yong‐Gui Zhou
Abstract
The development of chiral ligands to fine-tune the stereocontrol has been recognized as a crucial pillar of asymmetric catalysis. In contrast to the well-developed chiral pyridine–pyridine-type and pyridine–oxazoline-type ligands, chiral oxazole–pyridine-type ligands have rarely been exploited. In this study, a class of [2.2]paracyclophane-based planar-chiral oxazole–pyridine N, N -ligands have been designed and synthesized. These ligands presented a superior performance in the enantioselective palladium-catalyzed asymmetric acetoxylative cyclization of alkyne-tethered cyclohexadienones, providing the chiral cis -hydrobenzofurans that belong to bioactive molecules with potent NF-κB inhibition in broad substrate scope. These results demonstrated the promising potential of the chiral oxazole–pyridine ligands as an efficient type of N, N -ligand scaffold.