Epoxidation of Alkenes with Aqueous Hydrogen Peroxide and Quaternary Ammonium Bicarbonate Catalysts
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Epoxidation of Alkenes with Aqueous Hydrogen Peroxide and Quaternary Ammonium Bicarbonate Catalysts Jerrik Mielby • Søren Kegnæs
Received: 4 June 2013 / Accepted: 19 August 2013 / Published online: 4 September 2013 Ó Springer Science+Business Media New York 2013
Abstract A range of solid and liquid catalysts containing bicarbonate anions were synthesised and tested for the epoxidation of alkenes with aqueous hydrogen peroxide. The combination of bicarbonate anions and quaternary ammonium cations opens up for new catalytic systems that can help to overcome challenges with catalyst separation and reuse. Keywords Green chemistry Epoxidation Alkenes Oxidation Liquid-phase oxidation
Epoxides are among the most versatile intermediates in organic synthesis and find use in the production of many bulk commodities, high-valuable fine chemicals and pharmaceuticals [1]. Unfortunately, epoxides are often synthesized using stoichio-metric amounts of strong organic oxidants such as peracetic acid [2], tert-butyl hydroperoxide [3] or m-chloro-peroxy-benzoic acid [4]. These oxidants are not particularly attractive on an industrial scale because of the poor atom economy and concerns for safety. The development of effective catalytic oxidations and epoxidations using more environmentally friendly oxidants is therefore highly desirable [5, 6]. In particular, much effort has been devoted to the use of aqueous hydrogen peroxide [7]. Beside molecular oxygen [8, 9], hydrogen peroxide is
Electronic supplementary material The online version of this article (doi:10.1007/s10562-013-1088-1) contains supplementary material, which is available to authorized users. J. Mielby S. Kegnæs (&) Department of Chemistry, Technical University of Denmark, Kemitorvet 207, 2800 Kgs. Lyngby, Denmark e-mail: [email protected]
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the most attractive oxidant, because it is cheap, easy to handle and produces water as the only by-product [10]. During the last 30 years several efficient methods for the epoxidation of alkenes with hydrogen peroxide using Ti [11], V [12], Mn [13, 14], Fe [15], W [16, 17] and Re [18, 19] metal catalysts have been reported. However, most of these catalysts are homogeneous and requires tedious separation procedures to reuse the expensive catalysts. Immobilization of the homogeneous catalysts is challenging and may lead to decreased activity, poor stability and leaching of the catalytically active species. Although, titanium-containing zeolites such as TS-1 have become well-known as effective heterogeneous catalysts for the epoxidation of linear alkenes [11], the microporous catalysts generally suffer from diffusion limitations when it comes to more bulky substrates [20]. In 2000, Yao and Richardson [21] reported the bicarbonate-catalyzed epoxidation of alkenes with aqueous hydrogen peroxide. In this simple and metal-free system, the active oxidant was proposed to be the peroxymonocarbonate anion HCO4- formed by the reaction of HCO3with H2O2. Yao and Richardson found that bicarbonate activated peroxide (BAP) system could be
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