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N ‐Heterocyclic carbene/phosphite synergistically assisted Pd/C‐catalyzed Suzuki coupling of aryl chlorides
Author(s) -
Ke Haihua,
Chen Xiaofeng,
Zou Gang
Publication year - 2014
Publication title -
applied organometallic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.53
H-Index - 71
eISSN - 1099-0739
pISSN - 0268-2605
DOI - 10.1002/aoc.3076
Subject(s) - chemistry , carbene , aryl , catalysis , palladium , suzuki reaction , steric effects , medicinal chemistry , nitrile , organic chemistry , coupling reaction , combinatorial chemistry , alkyl
An N ‐heterocyclic carbene and phosphite synergistically enhanced Pd/C catalyst system has been developed for Suzuki coupling of aryl chlorides and aryl boronic acids from commercially available Pd/C with sterically demanding N , N ′‐bis(2,6‐diisopropylphenyl)imidazolylidene and trimethylphosphite. A remarkable increase in catalytic activity of Pd/C was observed when used along with 1 equiv. N , N ′‐bis(2,6‐diisopropylphenyl)imidazolium chloride and 2 equiv. phosphite with respect to palladium in appropriate solvents that were found to play a crucial role in Pd/C‐NHC‐P(OR) 3 ‐catalyzed Suzuki coupling . A dramatic ortho ‐substitution effect of carbonyl and nitrile groups in aryl chlorides was observed and explained by a modified quasi‐heterogeneous catalysis mechanism. The Pd/C catalyst could be easily recovered from reaction mixtures by simple filtration and only low palladium contamination was detected in the biparyl products. A practical process for the synthesis of 4‐biphenylcarbonitrile has therefore been developed using the N ‐heterocyclic carbene/phosphite‐assisted Pd/C‐catalyzed Suzuki coupling . Copyright © 2013 John Wiley & Sons, Ltd.