Green and Sustainable Chemistry, 2013, 3, 56-60 http://dx.doi.org/10.4236/gsc.2013.32010 Published Online May 2013 (http://www.scirp.org/journal/gsc) n-Dodecylbenzene Sulfonic Acid (DBSA) as a Novel Brønsted Acid Catalyst for the Synthesis of Bis(indolyl)methanes and Bis(4-hydroxycoumarin-3-yl)methanes in Water Balu Pawar 1 , Vinod Shinde 2 , Atul Chaskar 1* 1 Department of Chemistry, Sanghavi College of Engineering, Nashik, India 2 Pacific Academy of Higher Education & Research University, Udaipur, India Email: * achaskar25@gmail.com Received February 12, 2013; revised March 14, 2013; accepted March 22, 2013 Copyright © 2013 Balu Pawar et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. ABSTRACT n-Dodecylbenzene sulfonic acid (DBSA) as a novel, biodegradable, and efficient Brønsted acid catalyst used for the reaction of indoles/4-hydroxy coumarin with aldehydes to obtain a bis(indolyl)methanes/bis(4-hydroxycoumarin-3- yl)methanes, respectively. The catalyst exhibited remarkable activity, and tolerated a wide variety of functional groups providing the desired bis(indolyl)methanes and bis(4-hydroxycoumarin-3-yl)methanes in good to excellent yield (70% - 96%) in water. Keywords: n-Dodecylbenzene Sulfonic Acid (DBSA); Indole; Aldehyde; Bis(indolyl)methane; Bis(4-hydroxycoumarin-3-yl)methanes 1. Introduction Heterocyclic compounds, the highly popular precursor molecules are extensively employed in food, cosmetic and pharmaceutical industries for their broad range of biological activities [1-3]. In pharmaceutical industries coumarin, indole and their derivatives have received great attention due to their therapeutic potential for anti- biotic, anti-inflammatory, anti-coagulant, analgesic, anti- tumor, anti-HIV, anti-apoptotic, cytotoxic, anti-oxidant and insecticidal activities [4-12]. Moreover bis(indolyl) methane derivatives are used as sensors for Cu 2+ ions [13]. Bis(indolyl)methanes and bis(4-hydroxycoumarin- 3-yl) methanes are obtained by the condensation of two molecules of indoles or 4-hydroxy coumarin with one molecule of aldehyde or ketone in the presence of a Lewis acid or Brønsted acid catalyst. Literature reports revealed that the Lewis acid catalysts are deactivated or decomposed by the presence of nitrogen in the reactants. Hence, it necessitates having more than stoichiometric amounts of Lewis acid in the reaction mixture [14]. Hitherto, numbers of methods are in use for synthesis of all these biologically active molecules [15-23]. Some of these methods show advantages with respect to each other. Many of these protocols require stoichiometric and expensive catalyst, prolonged reaction time, high tem- perature, harsh reaction conditions use of organic sol- vents, tedious and laborious workup procedure, etc. The failure in removal of water formed during the course of reaction leads to low yields of products. Nowadays, with the awareness towards the environ- ment, researchers are emphasizing on finding out the methods that will fulfill the criteria of environment friendly green chemistry methodologies. In this line, very recently, Thakur et al. [24] used phosphate-impregnated titania catalyst under solvent free condition. Kalita and co-workers [25] used Indion Ina 225 H resin for synthe- sis of bisindolyl methane. In our recent work, we have used silica supported sodium hydrogen sulfate and Indion 190 resin for the synthesis of bis(4-hydroxycoumarin-3- yl)methanes [26]. Performing the reactions in micellar media instead of organic solvents can alter the reaction rates and the path- ways of the reactions. Due to the “local concentration effect” Micelles can concentrate the reactants within their small volumes, stabilize substrates, intermediates or pro- ducts and orient substrates. A reactant may align at the * Corresponding author. Copyright © 2013 SciRes. GSC