Abstract
In the quest for efficient and recyclable heterogeneous catalysts for Sonogashira coupling reactions, a PEG-OMe (Methoxy Polyene Glycol) - mediated method was developed to immobilize Pd/Cu bimetallic nanoparticles on activated carbon (AC). Catalytic experiments showed that Pd/Cu@AC prepared in a PEG-OMe 500 had the highest activity. The morphology and composition of the catalyst were determined, and the identified crystallized and heterometallic nanoparticles of Pd/Cu were essential for an efficient catalytic cycle. The Pd/Cu@AC catalyst was successfully used in Sonogashira reactions (21 examples) including with aryl bromides as the coupling partner in EtOH at 80–100 °C. The catalyst was recycled at least nine times.
Highlights
The Csp–Csp2 cross-coupling reaction, known as a Sonogashira reaction, has gained much attention because alkynes are important precursors of various pharmaceuticals, natural products, and organic materials [1,2,3]
In the putative catalytic cycle of a Sonogashira reaction, Pd and Cu are responsible for the oxidative addition of a C–X bond and the transmetalation of an activated triple bond, respectively [15,16]
In ethanol (Cat 1), only Pd0 deposited on the activated carbon (AC) support
Summary
The Csp–Csp cross-coupling reaction, known as a Sonogashira reaction, has gained much attention because alkynes are important precursors of various pharmaceuticals, natural products, and organic materials [1,2,3]. Several Pd/Cu bimetallic nanoparticles (NPs) were loaded on commercially available insoluble organic or inorganic supports as heterogeneous catalysts, and were successfully used in cross-coupling reactions and other chemical reactions [22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39]. It is essential to develop solid-supported Pd/Cu bimetallic NP heterogeneous catalysts using available raw materials and simple procedures and with a high catalytic efficiency
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