Melamine Trisulfonic Acid as a New, Efficient and Reusable Catalyst for the Solvent Free Synthesis of Coumarins

Coumarins and their derivatives are important classes of heterocyclic compounds whose synthesis has been the focus of attention of many organic and medicinal chemists. Such an interest in these compounds can be attributed to their variety of bioactivities such as, inhibition of platelet aggregation [1], antibacterial [2], anticancer [3], inhibitor of steroid 5αreductase [4] and inhibitor of HIV-1 protease [5]. They are widely used as additives in food, perfumes, agrochemicals, cosmetics, pharmaceuticals [6] and in the preparation of insecticides, optical brightening agents, dispersed fluorescent and tunable dye lasers [7]. Coumarins also act as intermediates for the synthesis of fluorocoumarins, chromenes, coumarones, and 2-acylresorcinols [8]. A variety of methods including Pechmann [9], Knoevenagel [10], Reformatsky [11], Perkin [12] and Wittig [13] reactions and flash vacuum pyrolysis [14] have been used for the synthesis of coumarins of which the Pechmann reaction is the most common procedure. Generally, the Pechmann reaction is carried out by the