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Palladium Complexes of N‐Heterocyclic Carbenes as Catalysts for Cross‐Coupling Reactions—A Synthetic Chemist's Perspective
Author(s) -
Kantchev Eric Assen B.,
O'Brien Christopher J.,
Organ Michael G.
Publication year - 2007
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.200601663
Subject(s) - palladium , catalysis , steric effects , chemistry , coupling reaction , ligand (biochemistry) , reductive elimination , combinatorial chemistry , oxidative addition , carbene , transmetalation , coupling (piping) , computational chemistry , organic chemistry , materials science , biochemistry , receptor , metallurgy
Palladium‐catalyzed CC and CN bond‐forming reactions are among the most versatile and powerful synthetic methods. For the last 15 years, N‐heterocyclic carbenes (NHCs) have enjoyed increasing popularity as ligands in Pd‐mediated cross‐coupling and related transformations because of their superior performance compared to the more traditional tertiary phosphanes. The strong σ‐electron‐donating ability of NHCs renders oxidative insertion even in challenging substrates facile, while their steric bulk and particular topology is responsible for fast reductive elimination. The strong PdNHC bonds contribute to the high stability of the active species, even at low ligand/Pd ratios and high temperatures. With a number of commercially available, stable, user‐friendly, and powerful NHC–Pd precatalysts, the goal of a universal cross‐coupling catalyst is within reach. This Review discusses the basics of Pd–NHC chemistry to understand the peculiarities of these catalysts and then gives a critical discussion on their application in CC and CN cross‐coupling as well as carbopalladation reactions.