Synthesis of a Cellulosic Pd(salen)-Type Catalytic Complex as a Green and Recyclable Catalyst for Cross-Coupling Reactio
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Synthesis of a Cellulosic Pd(salen)‑Type Catalytic Complex as a Green and Recyclable Catalyst for Cross‑Coupling Reactions Peng Sun1,2 · Jiaojiao Yang1 · Chunxia Chen1,2 · Kaijun Xie1 · Jinsong Peng1 Received: 25 November 2019 / Accepted: 8 March 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract A green recyclable cellulose-supported Pd(salen)-type catalyst was synthesized through sequential three steps: chlorination with thionyl chloride, modification by ethylenediamine, and the formation of Schiff base with salicylaldehyde to immobilize palladium chloride through multiple binding sites. This novel heterogeneous cellulosic Pd(salen)-type catalytic complex was fully characterized by FT-IR, SEM, TEM, XPS, ICP-AES and TG. The traditional cross-coupling chemistry, such as Suzuki, Heck, Sonogashira, Buchwald–Hartwig amination and etherification, was then investigated in the presence of the above cellulose-palladium nanoparticle. Studies have shown that the synthesized catalyst shows high activity and efficiency for all types of transformations, providing the corresponding carbon–carbon or carbon–heteroatom coupling products in a general and mild manner. Furthermore, the catalyst demonstrates high to excellent yields and is easily recycled by simple filtration for up to twelve cycles without any significant loss of catalytic activity. Graphic Abstract Ar
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Keywords Cellulose · Salen-type ligand · Pd catalysis · Heterogeneous · Cross-coupling reactions Electronic Supplementary Material The online version of this article (https://doi.org/10.1007/s10562-020-03172-5) contains supplementary material, which is available to authorized users. Extended author information available on the last page of the article
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1 Introduction Pd-catalyzed cross-coupling reactions, such as Suzuki–Miyaura, Heck, Sonogashira, Buchwald–Hartwig amination and etherification, have emerged as powerful tools for carbon–carbon and carbon–heteroatom bond formation in synthetic organic chemistry [1, 2], displaying broad applications in the preparation of materials, natural products and biologically active compounds [3, 4]. Generally, these coupling reactions are carried out in the presence of a homogeneous palladium catalyst. However, the high costs associated with palladium and ligands, the difficulties in product separation and recycling of the catalyst, and the lack of generality toward all types of crosscoupling reactions obviously do not meet the prospects of contemporary green and sustainable chemistry development [5, 6]. To overcome these disadvantages, researchers have turned to the design and development of palladium complexes with broader activity immobilized on environmentally benign
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