Monodisperse Ni@Pd Core@Shell Nanoparticles Assembled on Reduced Graphene Oxide as a Highly Efficient and Reusable Heterogeneous Catalyst for the C–H Bond Arylation of Imidazo[1,2-a]pyridine with Aryl Halides

Abstract

We report herein, for the first time, the direct C–H bond arylation of imidazo­[1,2-a]­pyridine with aryl halides using monodisperse Ni@Pd core@shell nanoparticles assembled on reduced graphene oxide (rGO) as a highly efficient and reusable heterogeneous catalyst. Monodisperse Ni@Pd core@shell nanoparticles (NPs) were synthesized by using one-pot successive reduction of metal precursors in the presence of oleylamine and trioctyl phosphine and then assembled on rGO via a liquid-phase self-assembly method to yield rGO-Ni@Pd nanocatalyst. The structures of the colloidal Ni@Pd core@shell NPs and rGO-Ni@Pd nanocatalyst were characterized by TEM, high-resolution TEM (HR-TEM), STEM-EDS, XPS, and ICP-MS. Next, rGO-Ni@Pd nanocatalysts as well as rGO-Ni and rGO-Pd counterparts were first tested in the direct C–H bond arylation of imidazo­[1,2-a]­pyridine with bromobenzene under tunable reaction conditions to find the optimum reaction conditions. Under the optimum reaction conditions, the substrate scope of rGO-Ni@Pd-catalyzed direct C–H arylation of imidazo­[1,2-a]­pyridine was examined by performing the catalytic reactions with a variety of aryl halides. These studies showed for the first time that rGO-Ni@Pd nanocatalysts are highly efficient and reusable catalysts in the direct C–H bond arylation reactions and have a high potential to be applied in other C–H activation reactions.

Carbon‐Support‐Based Heterogeneous Nanocatalysts: Synthesis and Applications in Organic Reactions

“…Kilic et al. reported a monodisperse Ni@Pd core@shell nanoparticles decorated over RGO as presented in Figure . Nickel (II) acetate tetrahydrate (Ni(ac) 2 ⋅4H 2 O) and, palladium(II) bromide (PdBr 2 ) were used as metal precursor for the synthesis of monodisperse Ni@Pd core@shell nanoparticles.…”

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

“…Successful C–H activation without using any directing group was an added advantage of this protocol. The group of Kilic and Turgut have developed an efficient direct C–H bond arylation reaction of imidazo[1,2- a ]pyridines [227]. Aryl halides were used as an arylating agent and the reaction was catalyzed by monodispersed Ni@Pd core@shell NPs assembled on reduced graphene oxide (rGO) (rGO-Ni@Pd) as heterogeneous catalyst (Scheme 190).…”

Monodisperse CuPd alloy nanoparticles as efficient and reusable catalyst for the C (sp2)–H bond activation

“…Graphene‐supported bimetallic nanoparticles are promising nanocatalysts, which can show strong and tunable catalytic activity and selectivity. Reduced graphene oxide supported alloy nanoparticles such as AuPd@rGO, [ 28–30 ] AgPd@rGO, [ 31–33 ] NiPd@rGO, [ 34,35 ] CuPd@rGO, [ 36–39 ] and monodisperse NiPd core shell nanoparticles (rGO‐Ni@Pd) [ 40 ] have been found potential applications in numerous fields, such as hydrogenation, oxidation, intramolecular C–H arylation reactions, C–C cross‐couplings, hydrosilylation reactions, and electrocatalysis. Due to the synergistic effect of alloy nanoparticle and rGO support, these composite catalysts have superior performance compared with individual components.…”