Palladium nanoparticles immobilized on cyclodextrin‐decorated halloysite nanotubes: Efficient heterogeneous catalyst for promoting copper‐ and ligand‐free Sonogashira reaction in water–ethanol mixture

Abstract

Combining the excellent features of halloysite nanoclay and cyclodextrin, a novel hybrid system was designed and synthesized based on covalent attachment of tosylated cyclodextrin to thiosemicarbazide‐functionalized halloysite nanoclay and used for the immobilization of Pd nanoparticles. The resulting hybrid, Pd@HNTs‐T‐CD, was then characterized using various techniques, and successfully used for promoting copper‐ and ligand‐free Sonogashira coupling reactions of halobenzenes and acetylenes in a mixture of water and ethanol. Notably, under Pd@HNTs‐T‐CD catalysis, the reaction could proceed in relatively short reaction time to furnish the corresponding products in high yields. Additionally, the catalyst was recyclable and could be simply recovered and reused for several reaction runs. Results also established negligible leaching of Pd, indicating the efficiency of HNTs‐T‐CD for embedding Pd nanoparticles.

Solid-Supported Palladium Catalysts in Sonogashira Reactions: Recent Developments

“…Thus, a hybrid system based on covalent conjugation of tosylated cyclodextrin to thiosemicarbazide-functionalized halloysite nanotubes (PdNPs@CD-T-HNTs, 69) demonstrated to be effective in the coupling of several terminal acetylenes and halobenzenes (Scheme 9). The study confirmed a synergistic effect between HNTs and CD, being recycled up to 13 cycles with just a slight loss of activity [116]. A hybrid material has also been prepared using cyclodextrins and carbon nanotubes (CNTs) (PdNPs@CD-CNT), and has been used in the coupling of phenylacetylene and iodobenzene with high activity (93% yield of diphenylacetylene), the catalyst being recycled six times with only a slight loss of activity [117].…”

Effects of Basic Promoters on the Catalytic Performance of Cu/SiO2 in the Hydrogenation of Dimethyl Maleate

“…The catalysts for the hydrogenation of esters mainly include Ru [8][9][10][11], Pt [12], Pd [13,14], Cu [15][16][17][18], and so on. The noble metal catalysts, such as Ru, Pt and Pd [19,20], have the advantages of high activity, but their price is expensive. A supported Cu catalyst with a strong capacity for the The catalysts for the hydrogenation of esters mainly include Ru [8][9][10][11], Pt [12], Pd [13,14], Cu [15][16][17][18], and so on.…”

“…A supported Cu catalyst with a strong capacity for the The catalysts for the hydrogenation of esters mainly include Ru [8][9][10][11], Pt [12], Pd [13,14], Cu [15][16][17][18], and so on. The noble metal catalysts, such as Ru, Pt and Pd [19,20], have the advantages 2 of 10 of high activity, but their price is expensive. A supported Cu catalyst with a strong capacity for the adsorption, activation of C=O bond, and low hydrogenolysis activity of C-C bond, is cheap and easy to prepare-and then, it is widely used in ester hydrogenation reactions [21].…”

Palladated halloysite hybridized with photo‐polymerized hydrogel in the presence of cyclodextrin: An efficient catalytic system benefiting from nanoreactor concept

“…The study of the catalytic activity of these hybrid systems proved that they could benefit from the chemistry of both components, and the presence of CD as a phase transfer agent could increase the rate of the reactions in aqueous media. [23,24,44] Taking these results into account and considering the fact that despite the presence of hydroxyl groups on the surface of Hal, it still has a relatively weak adhesion with Pd nanoparticles due to the absence of chemical interaction, [19,27] design and preparation of a novel Hal-hydrogel catalytic system for hydrogenation of nitro arenes was targeted. It is assumed that the polymeric functionality on Hal not only can result in efficient immobilization of Pd nanoparticles due to the electrostatic reactions of Pd nanoparticles with many amide functionalities on the polymer backbone, but also the nano-environment aroused from polymer swelling in aqueous media could effectively concentrate the substrates and enhance the reaction rate.…”