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Low Pressure Flow Chemistry of CuAAC Click Reaction Catalyzed by Nanoporous AuCu Membrane Jiangwei Wen, Kun Wu, Dali Yang, Jun Tian, Zhiyuan Huang, Alexander S. Filatov, Aiwen Lei, and Xiao-Min Lin ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b06927 • Publication Date (Web): 23 Jul 2018 Downloaded from http://pubs.acs.org on July 24, 2018
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ACS Applied Materials & Interfaces
Low Pressure Flow Chemistry of CuAAC Click Reaction Catalyzed by Nanoporous AuCu Membrane Jiangwei Wen,†,‡ Kun Wu, †,‡ Dali Yang, † Jun Tian,†,‡ Zhiyuan Huang,† Alexander S. Filatov, § Aiwen Lei *,† and Xiao-Min Lin *,‡ †
The Institute for Advanced Studies (IAS), College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, Hubei 430072, P. R. China. ‡ Center for Nanoscale Materials, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA. § Department of Chemistry, The University of Chicago, 929 East 57th Street, Chicago, Illinois 60637, USA. KEYWORDS: Nanowire, Membrane, Click Chemistry, CuAAC, Catalyst ABSTRACT Click chemistry has been widely used in bioconjugation, polymer synthesis and the development of new anticancer drugs. Here, we report a nanoporous membrane made of AuCu alloy nanowires which can effectively catalyze copper (I)-catalyzed 1,3 dipolar cycloaddition between azide and terminal alkyne (CuAAC) in flow condition with pressure less than one bar. Comparison studies of the nanowires before and after the reaction using x-ray photoelectron spectroscopy reveal Cu(0) and Cu(I) are main species that promote the reaction. This simple strategy can be used to synthesize a variety of compounds with triazole linkage, and extended to gram level chemical production.
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CuAAC is a quintessential click reaction that is carried out under mild conditions and yield chemospecific products.1-4
Ever since its discovery independently by the groups of
Sharpless5 and Meldal,6 it has become one of the most reliable synthetic protocols in organic chemistry, material science and biomedical research.7-8 However, the traditional homogeneous Cu(I) catalysts used in CuAAC reaction face several challenges, with the main issue being the difficulty of separating the catalysts from reaction products. Consequently, the heterogeneous catalysts for CuAAC reaction are being actively investigated.9-11 Typically, copper (I) ions or Cu, Cu2O nanoparticles are grafted onto a series of host materials, including polymers, dendrimers, charcoal, mesoporous silica or zeolites, layered hydrotalcite, clays, polyoxometalates (POM) and metal-organic framework (MOF) solid materials.4, 12-17 Some of these catalysts show excellent conversion rate in CuAAC reaction. But under flow condition, significant amount of copper tends to leach out.9,
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Cu(0) NPs-catalyzed click reaction also requires the presence of
triethylamine as a base to facilitate the conversion of Cu(0) to soluble Cu(I) species,19 which tends to accelerate the dissolution of active catalysts. These observations stimulated a debate whether these systems are truly heterogeneous in nature.18 Furthermore, organic contaminants in polymeric matrix and dissolved Cu(I) species affect the purity of pharmaceutical compounds.20 As a result, heterogeneous CuAAC flow reaction typically requires a downstream scavenging unit to purify the reaction product.17 With these complex designs, many flow reactors need high pressure (up to 10 - 20 bar) to push the solvent through the catalyst column at a reasonable flow rate.18,
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It is thus highly desirable to develop a simpler, highly efficient and stable
heterogeneous catalyst that can be operated under low pressure continuous flow condition. Herein, we demonstrate a catalytic membrane created by depositing solution-synthesized AuCu nanowires onto a commercial filter support.
The porous membrane is formed by highly
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ACS Applied Materials & Interfaces
branched AuCu nanowires which allows an intimate contact between the reactants and catalyst surface. The AuCu alloy is also chemically more stable against surface oxidation than pure Cu. X-ray photoelectron spectroscopy (XPS) shows that the formation of relatively stable Cu(I)2O in the surface scale of alloy nanowire which provide the catalytic active sites to promote a CuAAC reaction. Alloying can also prevent significant leaching of active Cu species into the reaction medium. We demonstrate that this type of membrane can provide an efficient conversion of precursors with a high throughput under a low pressure (
