PEG-modified N-heterocyclic carbene ligands for highly efficient and recyclable Pd-catalyzed Heck reaction in water

An efficient Pd-NHC catalyst system in situ generated from Na2PdCl4 and PEG-functionalized imidazolium salts for Mizoroki-Heck reactions in water

Three PEG-functionalized imidazolium salts L1–L3 were designed and prepared from commercially available materials via a simple method. Their corresponding water soluble Pd–NHC catalysts, in situ generated from the imidazolium salts L1–L3 and Na₂PdCl₄ in water, showed impressive catalytic activity for aqueous Mizoroki–Heck reactions. The kinetic study revealed that the Pd catalyst derived from the imidazolium salt L1, bearing a pyridine-2-methyl substituent at the N3 atom of the imidazole ring, showed the best catalytic activity. Under the optimal conditions, a wide range of substituted alkenes were achieved in good to excellent yields from various aryl bromides and alkenes with the catalyst TON of up to 10,000.

N-Heterocyclic carbene ligands bearing poly(ethylene glycol) chains: effect of the chain length on palladium-catalyzed coupling reactions employing aryl chlorides

N-Heterocyclic carbenes bearing poly(ethylene glycol) chains of different lengths have been employed as ligands in palladium-catalyzed coupling reactions of aryl chlorides.