Melamine‐Based Microporous Network Polymer Supported Palladium Nanoparticles: A Stable and Efficient Catalyst for the Sonogashira Coupling Reaction in Water

Abstract

A template consisting of a melamine‐based microporous polymer network was synthesized and utilized as a solid support to stabilize palladium nanoparticles; the resulting Pd/SNW1 material showed good catalytic activity in copper‐free Sonogashira coupling in water. Various aryl iodides were efficiently coupled with arylacetylenes under very low catalyst loadings in an environmentally benign medium. Hot filtration tests confirmed the heterogeneity of the catalyst, which was reused under the optimized conditions without any significant change in its activity. This simple preparation of the catalyst, the stability of the catalyst, product selectivity, and easy recovery and regeneration indicate the possible utilization of this catalytic system in a multitude of catalyzed reactions and industrial processes.

Covalent triazine polymers using a cyanuric chloride precursor via Friedel–Crafts reaction for CO2 adsorption/separation

“…Recently, POPs which can be constructed from light-weight elements linked by strong covalent bonds have attracted increasing attention for gas adsorption, storages and separation owing to their high stability against moisture, chemical stability with long lifetimes and easy handling [15]. These are known by their different product designations, such as Schiff base networks (SNWs) [16], benzimidazole-linked polymers (BILPs) [17], covalent triazine frameworks (CTFs) [18], polymers with intrinsic microporosity (PIMs) [19], porous aromatic frameworks (PAFs) [20], porous polymer frameworks (PPFs) [21], porous polymer networks (PPNs) [22], covalent organic frameworks (COFs) [23], element-organic frameworks (EOFs) [24], covalent organic polymers (COPs) [25], hypercrosslinked and conjugated microporous polymers (HCPs and CMPs) [26,27], covalent imine polymers (CIP) [28], and nitrogen-doped porous carbon materials (NPCs) [29]. The relatively low cost synthesis of this class of nitrogen chloride-catalyzed Friedel-Crafts reaction [33].…”

Solid-Supported Palladium Catalysts in Sonogashira Reactions: Recent Developments

“…Its recyclability was being assayed in the coupling of iodobenzene and phenylacetylene, observing a decrease in the yield after six reaction cycles (from 91% to 85%), attributed to the aggregation of the formed PdNPs revealed by microscopy observations. Water has also been the employed solvent in the Sonogashira reaction when using as catalyst PdNPs immobilized on a melamine-based microporous network polymer [36]. Using this catalyst, differently substituted aryl iodides have been coupled to monoarylated acetylenes, the reaction being carried out using pyrrolidine as base, in water as solvent at 70 °C in 2 h. The recyclability was The radical polymerization of N-isopropylacrylamide (NIPAM) and potassium 4-acryloxyoyl) pyridine-2,6-dicarboxylate (PAP), crosslinked with N,N -methylenediacrylamide, gave rise to a pH-responsive hydrogel (PNIPAM-co-PPAP) which has been used for the immobilization of palladium(II) (18) (Figure 6) [35], a material that catalyzed the cross-coupling reaction of aryl iodides and bromides with phenylacetylene in water as solvent.…”

“…Its recyclability was being assayed in the coupling of iodobenzene and phenylacetylene, observing a decrease in the yield after six reaction cycles (from 91% to 85%), attributed to the aggregation of the formed PdNPs revealed by microscopy observations. Water has also been the employed solvent in the Sonogashira reaction when using as catalyst PdNPs immobilized on a melamine-based microporous network polymer [36]. Using this catalyst, differently substituted aryl iodides have been coupled to monoarylated acetylenes, the reaction being carried out using pyrrolidine as base, in water as solvent at 70 • C in 2 h. The recyclability was determined using the model coupling of iodobenzene and phenylacetylene, five consecutive runs being performed with very low decrease in the observed final yield (from 98% to 94%).…”

Pd and Pd Based Alloy Nanoparticles as Visible Light Photocatalysts for Coupling Reactions under Ambient Conditions

“…215,218 The Pd/SNW1 (melamine-based microporous polymer) showed decent catalytic 29 activity in copper-free Sonogashira coupling in water. 219 The coupling reaction was performed in the presence of base in water at 80 °C. The 100% conversion (98% selectivity) of iodobenzene was observed in the presence of the Pd/SNW1 as a catalyst.…”

“…The 100% conversion (98% selectivity) of iodobenzene was observed in the presence of the Pd/SNW1 as a catalyst. 219 Generally, the phosphine-assisted method is one of the well-established methods, 220 Then it is deprotonated with a base yielding anionic amido complex; which subsequently gives a 3-coordinate complex. Finally, it forms the C-N bond by coupling the aryl halide with the amine.…”