Highly Efficient, Recyclable Pd(II) Catalysts with Bisimidazole Ligands for the Heck Reaction in Ionic Liquids

Abstract

[reaction: see text] New Pd(II) complexes with bisimidazole ligands were prepared and proved to be effective catalysts for the Heck reaction under phosphine-free conditions using ionic liquids as solvents. This system could be recycled five times without any loss of catalytic activity.

Five‐Membered Heterocycles: 1,3‐Azoles

“…The sulfur, oxygen and pyrrolidine-type nitrogen atoms are less nucleophilic than a pyridine-type nitrogen atom and the latter is expected to be the dominant donor. For example, a palladium(II) bisimidazole complex was obtained from the reaction of Pd (cod)ClMe (cod¼cyclooctadiene) with equimolar amounts of 92 and proved to be an effective catalyst for the Heck reaction under phosphine-free conditions using ionic liquids as solvent (Scheme 10.34) [143]. Thiazole does not react with bromine or chlorine in an inert solvent, but thiazoles with an electron-releasing substituent in the 2 or 4-position are brominated at C5 [146].…”

Palladium‐Catalysed Direct Regioselective Synthesis of Cyclic Ketals from Electron‐Rich Olefins and Aryl Bromides in Ionic Liquids

“…[7] Herein, we report that the Heck arylation of hydroxyalkyl vinyl ethers by aryl bromides can be carried out in the ionic liquid 1-butyl-3-methylimidazoli-…”

A novel ionic liquid-supported Schiff base ligand applied in the Pd-catalyzed Suzuki–Miyaura coupling reaction

“…Thus, the development of phosphine-free recyclable catalysts is of great importance. [19][20][21][22] Most recently, much more attention has been focused on the synthesis of functionalized ionic liquids (FILs), via incorporation of additional functional groups such as amine, amide, nitrile, ether, alcohol, acid, urea or thiourea, etc. as a part of the cation and/or anion for task specific purposes.…”