%0 Journal Article
%T L-Tyrosine as an Eco-Friendly and Efficient Catalyst for Knoevenagel Condensation of Arylaldehydes with Meldrum＊s Acid in Solvent-Free Condition under Grindstone Method
%A G. Thirupathi
%A M. Venkatanarayana
%A P. K. Dubey
%A Y. Bharathi Kumari
%J Organic Chemistry International
%D 2012
%I Hindawi Publishing Corporation
%R 10.1155/2012/191584
%X We investigate L-Tyrosine as an efficient catalyst for the Knoevenagel condensation of arylaldehydes with meldrum＊s acid containing cyclic active methylene group in solvent-free condition under grindstone method at room temperature to produce substituted-5-benzylidene-2,2-dimethyl-[1,3]dioxane-4,6-diones 3(a每j). 1. Introduction Toda introduced a method called the grindstone method [1, 2]. In this method, solids are grounded together using a pestle and mortar to get the products. These reactions are more efficient selective than those carried out in the corresponding solutions. Developing green chemical methods is one of the most important purposes of organic synthesis. Organic synthesis in the absence of solvent is a powerful tool for the generation of structurally different molecules whose special selectivity arises great interest. Moreover, solvent-free reactions are faster, taking just a few minutes. This aspect is coupled with the lowering of the total costs of running a reaction without solvent and specially designed equipment, which could become a very impressive factor in industry. Carbon每carbon bond formation reaction is the most important reaction in organic synthesis [3每6]. The Knoevenagel condensation is one such reaction which facilitates C每C double-bond formation and has been widely used in synthesis of alkenes of biological significance [7每11]. These reactions are usually catalyzed by bases [12每17] such as primary and secondary amines and their corresponding ammonium salts; Lewis acids [18每20], zeolite [21每23], and ionic liquids [24每27] have also been added to the existing list of substances that assisted Knoevenagel condensation in organic synthesis. Knoevenagel condensation of meldrum＊s acid and aldehydes gives rise to substrates for variety of reactions [28]. They are used in cycloaddition reactions [29], 1,4-conjugate addition reactions and preparation of mono alkyl meldrum＊s acid derivatives [30], and preparation of deuterated carboxylic acid derivatives [31]. These derivatives are also used in the preparation of ketenes by 汐,汕-pyrolysis [32], which are then used for preparation of different compounds such as cyclobutadiene derivatives [33], 汐,汕-unsaturated esters [34], and 汐,汕-unsaturated amides [35, 36]. Tyrosine is known to be an efficient, bifunctional, zwitterionic, and ecofriendly catalyst. It is available in both the enantiomeric, (S)-Tyrosine and (R)-Tyrosine, forms. The two functional groups of tyrosine enable it to act both as an acid as well as a base catalyst in chemical condensation reactions. In this paper, we highlight
%U http://www.hindawi.com/journals/oci/2012/191584/