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Cooperative Acid–Base Effects with Functionalized Mesoporous Silica Nanoparticles: Applications in Carbon–Carbon Bond-Formation Reactions

Authors

  • Sankaranarayanapillai Shylesh Dr.,

    1. Fachbereich Chemie, Technische Universität Kaiserslautern, Erwin-Schrödinger-Strasse 52, 67663 Kaiserslautern (Germany), Fax: (+49) 631-2054647
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  • Alex Wagner,

    1. Fachbereich Chemie, Technische Universität Kaiserslautern, Erwin-Schrödinger-Strasse 52, 67663 Kaiserslautern (Germany), Fax: (+49) 631-2054647
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  • Andreas Seifert Dr.,

    1. Institut fur Chemie, Technische Universität Chemnitz, Strasse der Nationen 62, 09111 Chemnitz (Germany)
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  • Stefan Ernst Prof. Dr.,

    1. Fachbereich Chemie, Technische Universität Kaiserslautern, Erwin-Schrödinger-Strasse 52, 67663 Kaiserslautern (Germany), Fax: (+49) 631-2054647
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  • Werner R. Thiel Prof. Dr.

    1. Fachbereich Chemie, Technische Universität Kaiserslautern, Erwin-Schrödinger-Strasse 52, 67663 Kaiserslautern (Germany), Fax: (+49) 631-2054647
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Abstract

Acid–base bifunctional mesoporous silica nanoparticles (MSN) were prepared by a one-step synthesis by co-condensation of tetraethoxysilane (TEOS) and silanes possessing amino and/or sulfonic acid groups. Both the functionality and morphology of the particles can be controlled. The grafted functional groups were characterized by using solid-state 29Si and 13C cross-polarization/magic angle spinning (CP/MAS) NMR spectroscopy, thermal analysis, and elemental analysis, whereas the structural and the morphological features of the materials were evaluated by using XRD and N2 adsorption–desorption analyses, and SEM imaging. The catalytic activities of the mono- and bifunctional mesoporous hybrid materials were evaluated in carbon–carbon coupling reactions like the nitroaldol reaction and the one-pot deacetalization–nitroaldol and deacetalization–aldol reactions. Among all the catalysts evaluated, the bifunctional sample containing amine and sulfonic acid groups (MSN–NNH2–SO3H) showed excellent catalytic activity, whereas the homogeneous catalysts were unable to initiate the reaction due to their mutual neutralization in solution. Therefore a cooperative acid–base activation is envisaged for the carbon–carbon coupling reactions.

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