The Influence of Imidazolylidene Ligands with Bulky Resorcinarenyl Substituents on Catalysts for Suzuki–Miyaura Coupling

Abstract

Abstract PEPPSI‐type imidazolylidene palladium complexes having their carbenic ring N ‐substituted with an aryl ring and a cavity‐shaped unit [25,26,27,28‐tetrapropyloxycalix[4]aren‐5‐yl or 6(10),12(16),18(22)‐tetramethylenedioxy‐2,8,14,20‐tetrapentylresorcin[4]aren‐5‐yl (TPR)] have been prepared and assessed in Suzuki–Miyaura cross‐couplings. Remarkable efficiency in the coupling of aryl chlorides with sterically hindered arylboronic acids was observed for the carbene ligand having its N atoms (N1, N2) substituted by a mesityl and a TPR group, respectively. This good performance possibly arises from strong steric interactions between the pentyl‐substituted cavitand unit and the catalytic centre, which favours reductive elimination. Two of the imidazolium salts used for complex synthesis were characterised by X‐ray diffraction analysis.