Catalytic Oxidative Cleavage of C=N Bond in the Presence of Zeolite H-NaX Supported , as a Green Reagent

Abstract

Increasing awareness of environmental hazards forces chemists to look for “eco-friendly” reaction conditions. In this connection, the use of heterogeneous catalysts involving solid reagents supported on high surface area materials, obtained by introduction of the reagent onto or into an organic polymeric or an inorganic porous or layered support material meets the fundamental challenges in the protection of the environment. These supported reagents have advantages such as easy handling, good dispersion of active sites leading to improved reactivity, safer and milder reaction conditions and minimal pollution [1, 2]. Oximes, hydrazones, and semicarbazones are useful as preferred derivatives for the identification and characterization of carbonyl compounds [3]. Several reagents have been reported for the regeneration of the carbonyl groups from the mentioned derivatives [4– 9]. Although some of the methods involve mild reaction conditions, most of them require strong acidic media, long reaction time, a strong oxidizing agent (which causes over oxidation), and expensive and not readily available reagents. Anhydrous metallic nitrates with a bidentate covalent coordination and with the available lower intermediate oxidation state for the metal, find maximum reactivity, and wider applicability [10, 11]. Their use, however, in organic syntheses is limited by solubility problems. Laszlo et al. have used the K10-montmorillonite clay-supported copper(II) nitrate (claycop) and iron(III) nitrate (clayfen) for many of the organic reactions like oxidation of alcohols, oxidative coupling of thiols, hydrolytic cleavage of imine derivatives of carbonyl compounds, cleavage of tosylhydrazones, phenyl hydrazones, 2,4-dinitrophenylhydrazones and semicarbazones [12]. K10montmorillonite supported Thallium nitrate is used for the oxidative rearrangement of alkyl aryl ketones into alkyl aryl carboxylates [13]. Pyridinium chlorochromate [14], potassium dichromate [15] and sodium metaperiodate [16] are some alumina-supported oxidants used for the chemoselective oxidation of alcohols and sulfides. In this paper we report a general method for the oxidative cleavage of C=N to their carbonyl derivatives in excellent yields without using any microwave or ultrasonic irradiation. To the best of our knowledge, this is the first report using a zeolite-supported cupric nitrate as the reagent for the regeneration of carbonyl group from oximes, hydrazones and semicarbazones. Moreover, copper-salts are inexpensive, easy to handle and environmentally friendly.