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Abstract
The selective reduction of oximes with sodium borohydride (NaBH4) in the presence of nano Cu and charcoal was investigated. Cu nanoparticles are widely used as catalysts; efficacious catalyst: copper and copper alloy nanometer feature high efficacy and selectivity, and can be used as catalyst in some reactions. We have shown that NaBH4 in the presence of charcoal is an efficient protocol for the reduction of oximes. Reduction reactions were carried out in EtOH (5 mL) as solvent under reflux condition at 70-80°C. The product amines were obtained in high to excellent yields. The stereo-chemistry of the reduction by using nano Cu is distinctively different from the other methods.
Keywords: Reduction; Oxime; NaBH4; Nano-particle Cu; Charcoal
1. Introduction
Further development of the catalytic system will require advanced matrials that can selectively catalyze the specific chemical reactions with a high reactivity (Lim et al., 2010). Nanoparticles exhibit under high catalytic activity and chemical selectivity under mild conditions (Beller et al., 1996). A large number of reactions were catalyzed efficiently using nanoparticles (Roucoux et al., 2002). The extremely small sized particles maximized the surface area exposed to the reactant, allowing more reactions to occure at the same time, thus speeding up the process (Korta et al., 2009). Amines are important functional groups in a variety of biologically interesting materials, including biopolymers, drugs, and dyes (Miriyala et al., 2004).
Among the different procedures for their synthesis, reduction of oximes is particularly popular as it provides an efficient means to amine. NaBH4/CuSO4 (Rao et al., 2002), (Py) Zn (BH4)2 (Zeynizadeh et al., 2005), NaBH4/ZrCl4/Al2O3 (Zeynizadeh et al., 2011), NaBH3CN/M°Cl5/NaHSO.H2O (Kouhkan et al., 2011) are combination systems which have been reported for reduction of oximes, though most of the reported methods are useful and efficient however, some of them suffer from disadvantages such as using strongly acidic or basic reaction conditions, offering low reduction capability and solvents prolong reaction the reduction of oximes produces hydroxylamine compounds, use of expensive volatile organic times, and finally perform the reaction at high temperature. In organic synthesis, increasing attention is being focused on green chemistry (Practor et al., 2010) using environmentally benign reagents and conditions (Zeynizadeh et al., 2013), which often lead to clean, ecofriendly, and highly efficient protocols through the simplified workups....