Nano-MgO: An Efficient Catalyst for the Synthesis of Formamides from Amines and Formic Acid Under MWI
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Nano-MgO: An Efficient Catalyst for the Synthesis of Formamides from Amines and Formic Acid Under MWI M. B. Madhusudana Reddy • S. Ashoka G. T. Chandrappa • M. A. Pasha
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Received: 29 March 2010 / Accepted: 9 May 2010 / Published online: 25 May 2010 Ó Springer Science+Business Media, LLC 2010
Abstract Nano-MgO a basic catalyst was prepared by solution combustion technique. It was characterized by powder XRD, SEM, BET and TEM analyses. It was used as a catalyst for the study of microwave-assisted Nformylation of various aromatic and alkyl amines with formic acid under solvent-free conditions. Nano-MgO showed excellent catalytic properties and the reactions went to completion, within 1–2 min to give products in high yield (90–98%). The catalyst is recoverable quantitatively and re-cycled with almost consistent activity. This new nano catalyst has the advantages of higher yield, lower cost, reduced environmental hazards, and the procedure is highly convenient. Keywords Nano-MgO Amines Formic acid N-Formylation Neat reaction Microwaves
1 Introduction Formyl group has been used widely as amino-protecting group in peptide synthesis and formamides are important intermediates in organic synthesis [1]. They are used as precursors for the synthesis of isocyanide [2, 3], as intermediates for mono-methylation of primary amines [4] and in the synthesis of formamidines [5]. Other pharmaceutically important compounds such as fluoroquinolines [6],
M. B. M. Reddy S. Ashoka G. T. Chandrappa M. A. Pasha (&) Department of Studies in Chemistry, Bangalore University, Central College Campus, Bengaluru 560001, India e-mail: [email protected]
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substituted arylimidazoles [7], 1,2-dihydroquinolines [8], and nitrogen-bridged heterocycles [9] also require formamides. A number of formylating reagents as well as methods are available in the literature [10–24]. Acetic formic anhydride is a well known formylating reagent [10], but is sensitive to moisture. Formylation using chloral [11], activated formic acid in the presence of DCC [2], or EDCI [12], activated formic esters [13–15], ammonium formate in acetonitrile [16, 17], 2,2,2-trifluoroethyl formate [18], formic acid [19], ZnO [20] and polyethylene glycol [21, 22] have been used for this purpose. More recently, Akbari et al. [23] have reported catalyst-free N-formylation of amines using guanidine derived ionic liquids. Most of the available methods have limitations such as long duration, high temperature, and use of expensive, toxic reagents or catalysts. Microwave irradiation has been employed for a number of organic reactions to reduce the reaction rate and gain selectivity in the product formation, and to get products in high yields [24]. Further, nano sized particles are considered to be particularly attractive as catalysts for their high reactivity, due to larger surface area [25–27]. They can be easily recovered from the reaction mixture and recycled after activation, thereby rendering the process economically viable. Among heterogeneous basic catalysts, nano-M
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