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Calix[4]arene‐Supported N ‐Heterocyclic Carbene Ligands as Catalysts for Suzuki Cross‐Coupling Reactions of Chlorotoluene
Author(s) -
Frank Markus,
Maas Gerhard,
Schatz Jürgen
Publication year - 2004
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200300542
Subject(s) - chemistry , carbene , palladium , calixarene , catalysis , suzuki reaction , toluene , salt (chemistry) , chelation , polymer chemistry , medicinal chemistry , crystal structure , coupling reaction , organic chemistry , molecule
Stable N ‐heterocyclic carbenes are generated starting from 5,17‐(bis‐imidazolium)‐substituted calix[4]arenes. Addition of Pd(OAc) 2 to these carbenes leads to macrocyclic cis ‐palladium chelate complexes in which the distal bridging of the upper rim leads to a strong distortion of the calix[4]arene skeleton which was proven by X‐ray crystal structure determination. Using an in‐situ catalytic system consisting of a calixarene‐imidazolium salt, Cs 2 CO 3 as a base and a source of palladium, a species is formed which can be used to catalyse the Suzuki cross‐coupling of 4‐chloro toluene. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)