Recyclable Palladium-Loaded Hyperbranched Polytriazoles as Efficient Polymer Catalysts for Heck Reaction

Abstract

Two polytriazole-based hyperbranched polymers (HBPs) with different molecular weights were prepared by chain-growth Cu-catalyzed azide–alkyne cycloaddition (CuAAC) polymerization of an AB2 monomer. Subsequent chain-end-capping reactions with alkynyl-containing ligands, such as 2-ethynylpyridine, phenylacetylene and alkyne-terminated polyethylene glycol (ay-PEG), produced a small library of HBPs that were applied to complex with Pd­(OAc)2 and produce Pd-loaded HBP catalysts for efficient Heck reaction of iodobenzene and styrene. The effects of HBP terminal ligand groups and polymer molecular weights were explored on the Heck reaction performance. At the same molecular weight, the HBP-based catalyst with PEG or pyridyl terminal groups showed faster Heck reaction kinetics as comparing to those with phenyl terminal groups. Meanwhile, higher-molecular-weight polymer catalysts exhibited faster catalytic kinetics than lower-molecular-weight ones. Comparing to the small-molecule monotriazole ligands, these polytriazole-based HBPs demonstrated higher catalytic efficiency due to multigroup cooperative effect, confirming that the polytriazole cluster was a boosting ligand for the catalytic Heck reaction. These HBP catalysts exhibited good recyclability as the catalyst after five-time recycling still achieved over 90% conversion of the reaction substrate.

Pd- and Au-Induced Circular and Fibrous Polymer Gelation via Thiocarbonyl Groups and High Pd Catalyst Activity

“…Organic–inorganic hybrid materials, which consist of organic polymers containing inorganic metals dispersed at the nanometer scale, have generated a great deal of interest due to their unique properties such as flexibility, high transparency, high reactivity, and mechanical and thermal stabilities. − There are many uses for such hybrid materials. For example, metal-immobilized heterogeneous polymeric catalysts are of great utility since they can be separated easily by filtration after reaction and reused in subsequent reactions, while homogeneous metal catalysts usually require cumbersome and costly workup procedures to separate the metal catalyst from the products. − These advantages make heterogeneous catalysts more suitable for continuous flow operations than for batchwise processes in large-scale industrial syntheses. However, heterogeneous catalysts generally exhibit lower catalytic activity than homogeneous catalysts, because the catalytic reaction must proceed heterogeneously.…”

Light-Mediated Polymerization Induced by Semiconducting Nanomaterials: State-of-the-Art and Future Perspectives

“…Moreover, doping the SNMs with catalytic active metals such as Ni, Au, , Pd, , and Ru could favorably influence their charge transfer efficiency, enhance the spatial charge separation, and suppress the radiative charge recombination, , thus improving the photocatalytic catalytic performance of SNMs. ,, We believe that heterostructures/nanohybrids forming from conjugating noble metal NPs with semiconductors could also be applied for photopolymerization systems with the rationally designed mechanism.…”

Pd supported on locust bean gum as reusable green catalyst for Heck and Sonogashira coupling reactions and 4‐nitroaniline reduction under ultrasound irradiation

“…Different supports have been proposed in the coupling reaction such as synthetic silica-based supports, [9] metal oxides, [10] carbon nanotubes, [11] and ionic liquids. [12] However, different synthesis teams have examined the possibility of replacing these with more environmentally friendly natural supports such as cellulose, PLA, gum arabic, [13][14][15] hyperbranched polytriazoles, [16] guar gum, [17] pectin, [18] gelatin, [19] and pectin/gelatin. [20] The immobilization of organometallic catalysts, such as organopalladium, with solid supports has been widely used in various fields of organic synthesis.…”