Ullmann C-O coupling of sterically hindered secondary alcohols using excess amount of strongly coordinating monodentate ligands

A new effective copper catalyzed C-O coupling reaction using excess amount of strongly coordinating monodentate ligands was successfully developed. Among the DMAP-type monodentate ligands, 4-pyrrolidinopyridine afforded the best results. The developed reaction is widely applicable for the synthesis of various hindered or acyclic secondary alkyl-aryl ethers. In this study, a novel and remarkable acceleration of the coupling reaction using excess amount of monodentate ligands was discovered. (C) 2017 Elsevier Ltd. All rights reserved.