N‐Heterocyclic carbene/phosphite synergistically assisted Pd/C‐catalyzed Suzuki coupling of aryl chlorides

Abstract

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.

A highly active palladium(II)–bis(oxazoline) catalyst for Suzuki–Miyaura, Mizoroki–Heck and sonogashira coupling reactions in aqueous dimethylformamide

“…The exceptional catalytic activity observed with Pd‐BOX complexes can be attributed to both electronic and steric effects. Electronic effects are induced by the aromatic spacer and the oxazoline rings, which enrich the palladium centre in electrons . While the steric effects originate from the substituents on the oxazoline rings, they provide kinetic stability to the intermediate complex, which supports an effective reductive elimination .…”

Magnetite@MCM‐41 nanoparticles as support material for Pd‐N‐heterocyclic carbene complex: A magnetically separable catalyst for Suzuki–Miyaura reaction

“…After these catalytic reactions, our Magnetite@MCM-41@NHC@Pd catalyst has shown fanciful catalytic activity on the Suzuki-Miyaura reaction of various boronic acids and different aryl bromides. Comparing the activities of our catalyst with similar types of magnetic or nonmagnetic heterogeneous palladium catalysts in Suzuki reactions, [37,39,[77][78][79][80][81][82][83][84][85] it shows that the catalyst in this study has better catalytic activity and applications than many reported similar catalysts (Table 3). In the literature, [37,39,[77][78][79][80][81][82][83][84][85] the most of the Suzuki-Miyaura cross-coupling reactions catalyzed by similar types of catalysts require high temperatures for coupled product formation.…”

“…Ghorbani-Choghamarani et al [76] CMC-NHC-Pd (0.8 mol%), EtOH/H 2 O (1:1), 60 C, X = Br, X a = Cl 180, 300 a 94, 52 a Karimi and Akhavan [77] γ-Fe 2 O 3 -acetamidine-Pd, DMF, 100 C, X = Br 120, 30 b 92, 96 b Ke te al. [78] Cell-NHC-Pd (0.75 mol%), DMF/H 2 O (1:1), 80 C, X = Br 120 99 Khajehzadeh and Moghadam [79] Pd/C-NHC-P (OR) 3 (0.03 mol%), EtOH, 80 C, X = Br 60 98…”

Development of the Applications of Palladium on Charcoal in Organic Synthesis

“…Moreover, the homogeneous Pd leached from Pd/C as the reaction occurred and was then deposited back onto the surface of activated carbon, which was clarified by the time‐course study. For the Suzuki–Miyaura coupling of the more practical aryl chlorides, Pd/C‐catalyzed Suzuki coupling of aryl chlorides and arylboronic acids has been revealed by Zou's group . 32 kinds of aryl chlorides were suitable partners for the C–C coupling reaction with good yields by addition of a synergistic σ‐donor and π‐acceptor pair of ligands: trimethylphosphite and N , N′ ‐bis(2,6‐diisopropylphenyl)imidazolylidene.…”