Cu nanoparticles immobilized on montmorillonite by biquaternary ammonium salts: a highly active and stable heterogeneous catalyst for cascade sequence to indole-2-carboxylic esters

Abstract

Cu-Q-MMT catalyst was prepared by immobilizing Cu nanoparticals on the biquaternary ammonium salts modified montmorillonite and exhibited high activity for cascade sequence to indole-2-carboxylic esters.

Palladium and Copper: Advantageous Nanocatalysts for Multi-Step Transformations

“…Tacrine derivatives are among the most investigated molecules Scheme 42. Cu-catalyzed cascade sequence for the synthesis of indole-2-carboxylic esters [178].…”

“…Contrary to homogeneous Cu-based catalysts generally used in the synthesis of indole-2-carboxylic esters, CuNPs can facilitate the metal separation from organic products, particularly important for biological applications. Zhou et al synthesized CuNPs on ammonium-functionalized montmorillonite (AF-MMT) [ 178 ]. AF-MMT retained its layered structure after metal loading and could be easily dispersed in polar solvents.…”

Copper(II) Oxide Nanoparticles Impregnated on Melamine‐Modified UiO‐66‐NH2 Metal–Organic Framework for C–N Cross‐Coupling Reaction and Synthesis of 2‐Substituted Benzimidazoles

“…When the reaction was performed in a solvent-free conditions, no progress in the reaction was observed ( Table 1, entry 1). The effect of the base such as KOH, NaOH, K 2 CO 3 , KHCO 3 , NaHCO 3 , Na 2 CO 3 on the reaction performance was studied ( Table 1, entry [12][13][14][15][16]. KOH gave the highest yield among the studied bases.…”

“…Copper as an abundant and inexpensive element, compared with noble metals (e.g. Pd), has been widely used for catalyzing organic reactions such as photodecarboxylation, click azide‐alkyne cycloaddition , C–C cross‐coupling reaction of Suzuki–Miyaura and Stille and Sonogashira–Hagihara , alkynylation of tetrahydroisoquinoline , C–O cleavage/C–N formation for synthesis of indazolo[3,2‐ b ]quinazolinones , allylic C–H oxidation of cyclic olefins , aerobic oxidation of alcohols , oxidative amidation of methylarenes , and also synthesis of carbonyl dibenzofurans , â‐enamino esters , ynones , quinoxalines , polysubstituted pyridines , and indole‐2‐carboxylic esters .…”

Fabrication of hybrids of zeolitic imidazolate frameworks supported zero‐valent copper nanoparticles as a non‐noble catalyst with high efficiency

“…Driven by economic consideration and environmental concern, design and fabrication of non-noble metal catalyst with high activity is becoming increasingly important [16,17]. Cu based composites are receiving more and more attention due to its abundant resources, environmental compatibility and excellent catalytic activities [9,[18][19][20][21][22][23][24]. However, the aggregation of metal NPs during reaction usually leads to the rapid decrease of catalytic activity and the recycle process of these small catalysts are very difficult [25,26].…”