%0 Journal Article
%T An Efficient and Green Method for Synthesis of 2,4,5-Triarylimidazoles without Use of Any Solvent, Catalyst, or Solid Surface
%A Swati Samanta
%A Saheli Sarkar
%A Rammohan Pal
%A Asok K. Mallik
%J Organic Chemistry International
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/512074
%X An efficient and green method for synthesis of 2,4,5-triarylimidazoles without use of any catalyst or solvent has been developed simply by heating (at 130¡ãC) of mixtures of 1,2-diketone, aromatic aldehyde, and ammonium acetate in 1£¿:£¿1£¿:£¿3 mole ratio. 1. Introduction Multicomponent reactions (MCRs) have emerged as a powerful tool for convergent synthesis of many complex organic molecules [1¨C6]. They are one-pot processes bringing together three or more components in a particular sequence of reactions and show high atom economy and remarkable selectivity. Because of their operational simplicity, MCRs have occupied a very prominent place in diversity oriented synthesis which is an important requirement for drug discovery. The imidazole nucleus is a rich source for getting biologically important organic molecules. Compounds containing imidazole moiety show a range of pharmacological properties and play important roles in biochemical processes. Various substituted imidazoles act as inhibitors of P38 MAP kinase [7] and B-Raf kinase [8], glucagon receptors [9], pesticides [10], fungicides [10], herbicides [11], and antitumor [12], anti-inflammatory [13], and antithrombotic [14] agents. Moreover, they are used in photography as photosensitive compounds [15]. 2,4,5-Triarylimidazoles (3) form an important group of substituted imidazoles having many of the above biological activities and material properties. Retrosynthetic analysis of 3 suggests the readily available compounds aromatic 1,2-diketones, aromatic aldehydes, and ammonia as their precursors. This has led to the development of a large number of synthetic methods for 3 using these simple starting materials. Almost all of these methods use ammonium acetate as the ammonia source. Many of the reported methods require long reaction time and use of expensive catalysts and organic solvents [16¨C23]. The current literature shows that there has been a growing trend towards green synthesis of these compounds [24, 25]. However, in such reported green methods, also use of catalysts or organic solvents could not be avoided. The current trend towards development of catalyst-free and solvent-free reaction conditions for organic synthesis [26, 27] encouraged us to study the same reaction under thermal condition without using any solvent or catalyst. The remarkable success in this endeavor is presented herein. 2. Results and Discussion Our present method involves subjecting of an intimate mixture of 1,2-diketone, aromatic aldehyde, and ammonium acetate in 1£¿:£¿1£¿:£¿3 mole ratio directly to heat (130¡ãC, 3¨C6£¿h). A range of
%U http://www.hindawi.com/journals/oci/2013/512074/