A mild oxidative method for the preparation of c-hydroxy-a-nitroolefins from a,b-epoxyketoximes using IBX Alba Souto, Jaime Rodríguez * , Carlos Jiménez * Departamento de Química Fundamental, Facultade de Ciencias, Campus da Zapateira, Universidade da Coruña, 15071 A Coruña, Spain article info Article history: Received 21 September 2009 Revised 15 October 2009 Accepted 19 October 2009 Available online 23 October 2009 Keywords: a,b-Epoxyketoximes c-Hydroxy-a-nitroolefins Oxidation Hypervalent iodine IBX DMP abstract An efficient method for the preparation of c-hydroxy-a-nitroolefins from a,b-epoxyketoximes has been developed using IBX. The reaction occurs at room temperature without the formation of over-oxidation products and also has an easy work-up procedure. Ó 2009 Elsevier Ltd. All rights reserved. The nitro group is particularly versatile in synthesis as it can be transformed into a plethora of functionalities. The Nef reaction, nucleophilic displacement, reduction to an amino group and con- version into a nitrile oxide are only some examples of the possible transformations. 1 More specifically, conjugated nitroolefins have found numerous applications in organic synthesis. 2 The character of these systems as electron-deficient alkenes allows easy 1,4- addition reactions and this opens the way to synthetically useful C–C and C–X (X = N, O) bond-forming reactions. 3 These compounds are also powerful dienophiles or dipolarophiles in cycloaddition reactions to generate new carbon–carbon single or double bonds. A number of methods have already been developed for the prepa- ration of nitroolefins, such as the nitroaldol (Henry) reaction, 4 but there is considerable interest in developing new and simple meth- ods for the preparation of this type of compound. On the other hand, organic derivatives of hypervalent iodine re- agents have found extensive applications in synthetic organic chemistry because of their selectivity, efficiency and simplicity of use. 5 Among these compounds, 2-iodoxybenzoic acid (IBX) is becoming the reagent of choice due to its ease of handling, stabil- ity/longer shelf life, tolerance to moisture and zero toxic waste generation. IBX was initially used for the oxidation of alcohols to carbonyl compounds, 6 but its synthetic value has been extended to a variety of other useful transformations. 7 The oxidative conversion of oximes into nitro functions using tri- fluoroperoxyacetic acid was reported a long time ago. 8 Some years later Takamoto et al. reported the transformation of a,b-epoxyke- toximes to c-hydroxy-a-nitroolefins using the same reagent. 9 The products were employed for the synthesis of 3-nitrocycloalkenones for use as dienophiles. 10 Furthermore, the oxidative elimination of a-haloketoximes using trifluoroperoxyacetic acid to give a-nitro- olefins has been reported. 11 However, the wider reactivity of the tri- fluoroperoxyacetic acid (Baeyer–Villiger oxidation, epoxidation of alkenes, etc.) narrowed the applications of this reagent in that chem- ical transformation. We report here a new oxidative method for the conversion of a,b-epoxyketoxime compounds to c-hydroxy-a-nitroolefins in good to moderate yields. The method employs IBX as a very mild oxidant that overcomes some of the disadvantages associated with the use of trifluoroperoxyacetic acid. Our method can be character- ised by two striking features: (a) easy work-up procedure, (b) the reaction occurs at room temperature without the formation of 0040-4039/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.tetlet.2009.10.090 * Corresponding authors. Tel.: +34 981 167000; fax: +34 981 167065. E-mail addresses: jaimer@udc.es (J. Rodríguez), carlosjg@udc.es (C. Jiménez). Scheme 1. Tetrahedron Letters 50 (2009) 7395–7398 Contents lists available at ScienceDirect Tetrahedron Letters journal homepage: www.elsevier.com/locate/tetlet