Cu/SBA-15 is an Efficient Solvent-Free and Acid-Free Catalyst for the Rearrangement of Benzaldoxime into Benzamide
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Cu/SBA-15 is an Efficient Solvent-Free and Acid-Free Catalyst for the Rearrangement of Benzaldoxime into Benzamide Ganji Saidulu • Narani Anand • Kamaraju Seetha Rama Rao Abhishek Burri • Sang-Eon Park • David Raju Burri
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Received: 15 July 2011 / Accepted: 24 September 2011 / Published online: 15 October 2011 Ó Springer Science+Business Media, LLC 2011
Abstract Cu/SBA-15 catalysts with various Cu loadings in the range of 5–20 wt% were prepared by an impregnation method and characterized by N2 adsorption, X-ray diffraction, temperature programmed reduction and X-Ray photoelectron spectroscopic techniques. Cu/SBA-15 catalysts are found to be highly active and selective for the Beckmann rearrangement of benzaldoxime into benzamide under solvent-free and acid-free conditions. Keywords Cu/SBA-15 Beckmann rearrangement Benzaldoxime Benzamide
1 Introduction Typically, amides are potential precursors for the synthesis of various natural products and drug intermediates [1]. The isomerization of oximes to amides (Beckmann rearrangement) is one of the most straightforward synthetic routes for the production of amides [2]. However, in the Beckmann rearrangement, migration of alkyl or aryl group is facile rather than hydrogen. Hence it is not a general process for the transformation of aldoximes into primary amides [3]. Furthermore, Beckmann rearrangement (BR) generally requires high reaction temperature and strong acidic and dehydrating media [3]. Despite of these G. Saidulu N. Anand K. S. R. Rao D. R. Burri (&) Catalysis Laboratory, Indian Institute of Chemical Technology, Hyderabad 500 607, India e-mail: [email protected] A. Burri S.-E. Park (&) Department of Chemistry, Laboratory of Nano-green Catalysis, Inha University, Incheon 402-751, Korea e-mail: [email protected]
impediments in the Beckman rearrangement of aldoximes into primary amides, the recent efforts in getting considerable conversions and selectivities are worth noting. For instance, metal catalyzed approach for the rearrangement of aldoximes into primary amides involving the sequential dehydration and hydration via nitrile intermediate formation exhibited substantial improvements [4]. Williams and his co-workers revealed the successful conversion of aldoximes into primary amides using Ru and Ir metal complexes [4, 5]. It is proved that Rh complexes are good candidates for the rearrangement of aldoximes to primary amides [6–8]. However, Rh, Ir, and Rh containing catalytic materials are highly expensive and in addition, usage of these catalysts requires laborious workup procedure to separate the product. Furthermore, use of environmentally and biologically harmful solvents is one of the main difficulties in these chemical transformations. In a recent report, solvent-free and acid-free Au/Ag co-catalysts are disclosed for the effective conversion of aldoximes to primary amides [9]. However, these Au/Ag co-catalysts are homogeneous in nature. In one of the reports, alumina supported rhodium hydroxide catalysts are used successfully as heterogeneou
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