Short Communication Efficient conversion of aldehydes and ketones into oximes using a nanostructured pyrophosphate catalyst in a solvent-free process Abdelhakim Elmakssoudi a , Karima Abdelouahdi b , Mohamed Zahouily a, c, ⁎, James Clark d , Abderrahim Solhy a, ⁎ a MAScIR Foundation, VARENA Center, Institute of Nanomaterials& Nanotechnology, ENSET, Av. De l'Armé Royale, Madinat El Irfane 10100‐Rabat, Morocco b Centre National pour la Recherche Scientifique et Technique (CNRST), Division UATRS, Angle Allal Fassi/FAR, B.P.8027, Hay Riad, 10000 Rabat, Morocco c Laboratoire de Catalyse, Chimiométrie et Environnement, URAC 24, Faculté des Sciences et Techniques, Université Hassan II, Mohammedia B. P. 146, 20650, Morocco d Green Chemistry Centre of Excellence, University of York, York YO10 5DD, UK abstract article info Article history: Received 10 July 2012 Received in revised form 9 September 2012 Accepted 13 September 2012 Available online 20 September 2012 Keywords: Heterogeneous catalysis Nanostructured pyrophosphate Clean synthesis Oximes Microwave Conventional heating A nanostructured pyrophosphate (Na 2 CaP 2 O 7 ) was synthesized by controlling the speed of its calcination, and then characterized by several methods including TGA, X-ray diffraction, FTIR, SEM, TEM and the determi- nation of the surface area by the BET method. However, several aldehydes and ketones were efficiently and rapidly converted into the corresponding oximes by treatment with hydroxylamine hydrochloride in a solvent-free process under microwave irradiation using this nanostructured pyrophosphate as catalyst. The yields of the products were very high and the time required for their preparation was very short compared to conventional heating experiments and the catalyst was efficiently re-used. © 2012 Elsevier B.V. All rights reserved. 1. Introduction One of the most important challenges for the modernization of organic synthesis is the preparation of active, selective, robust, and low-cost catalysts. Thus, the development of nanostructured catalysts for fine chemical production is currently a subject of increasing inter- est [1–4]. The second approach to achieve this target is to explore alternative reaction conditions and reaction media with minimal by-products [5]. Specifically, microwaves (MW) are an important alternate source of energy, which can accelerate reactions by the selective absorption of MW energy by polar molecules. The short reaction time and the expanded reaction range offered by MW assisted synthesis are suited to meet the increased demands in indus- try, particularly the pharmaceutical industry [6–8]. On the other hand, a large number of pharmaceutical oximes con- tain a group attached to a variable structure [9,10]. Furthermore, oximes are widely used as intermediates in fine organic synthesis [11–13]. The classical method for preparing them is the reaction of an aldehyde or ketone with hydroxylamine hydrochloride [14]. Sev- eral methods for their preparation have been reported in the litera- ture including the use of formic acid [15], pyridine-chloroform [16], ethanol-pyridine [17], sulfuric acid [18], and NaOH with or without solvent [19–22]. However, the hazardous nature of these reagents results in many limitations. In order to avoid these limitations, many alternative strategies have recently been developed using solid catalysts such as alumina [23], silica gel [24], basic Al 2 O 3 [25], resin (Amberlyst A-21) in ethanol [26], CaO [27], FeCl 3 [28], TiO 2 /SO 4 2- without solvent [29], supported-POM [30], and Na 2 SO 4 under ultrasound irradiation [31–33]. Recent literature has reported that high yields of hydroxyiminocycloalkanes could be achieved by either treating corre- sponding ketones with hydroxylamine or treating its salts in ionic liquids that contain sodium acetate or sodium bicarbonate [34]. Zang et al. have synthesized these products by the action of an ionic liquid under ultrasound irradiation [35]. More recently, Liao et al. have used the Pd/CNTs (carbon nanotubes) in the hydrogenation of nitrocyclohexane to cyclohexanone oxime [36]. Furthermore, many studies have been published describing the synthesis and use of the pyrophosphate (Na 2 CaP 2 O 7 ) in various fields, particularly in heterogeneous catalysis [37]. Bennazha et al. were able to synthesize and characterize a series of pyrophosphates by adopting a dry technique [38]. Recently, we have developed a method to tailor the nanostructure of this pyrophosphate by focus- ing on reactant crashing and the speed of calcination. This nano- structured pyrophosphate has been used with great success to catalyze the synthesis of 2-amino-chromenes [39]. In this paper and in the continuity of our work we wish to report a new, simple, Catalysis Communications 29 (2012) 53–57 ⁎ Corresponding authors. Tel.: +212 661379886; fax: +212 530279827. E-mail addresses: m.zahouily@mascir.com (M. Zahouily), a.solhy@mascir.com (A. Solhy). 1566-7367/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.catcom.2012.09.017 Contents lists available at SciVerse ScienceDirect Catalysis Communications journal homepage: www.elsevier.com/locate/catcom