A.Tzani, A. Douka, A. Papadopoulos, T. Kosanovic, E.Α. Pavlatou, E. Voutsas, A. Detsi
3rd International Symposium on Green Chemistry for Environment, Health and Development (2012), October 3-5, Skiathos Island-Greece (oral)
Green chemistry possesses the spirit of sustainable development and is attracting increasing interest in the 21st century. In the chemical world, strategies for increasing sustainability often require the redesign of reactions and modifications of existing chemical processes aiming, among other things, at the reduction of chemicals used as solvents in a wide range of industrial applications. In this context, ionic liquids (ILs) have recently emerged as a potential replacement for toxic, hazardous flammable and highly volatile organic solvents (VOCs) owing mainly to their negligible volatility, excellent thermal stability, and the variety of structures available. However in order to confidently label this class of solvents as ‘‘green’’, their effect on the environment must be thoroughly examined through biodegradation studies. ILs have been increasingly exploited in the pharmaceutical industry in various applications, such as drug formulations, solvents for the solubilization of drugs and for the synthesis of active pharmaceutical ingredients. In the frame of a research which examines the possibility of using task-specific ILs for developing green methodologies towards novel bioactive compounds, we present here preliminary results from the synthesis of ILs derived from ethanolamine and organic carboxylic acids and their application in the synthesis of 4-hydroxy-bis-coumarins possessing antioxidant activity. Three ILs were synthesized namely N-hydroxyethylammonium formate, acetate and trifluoroacetate and were used as solvents for the reaction between 4-hydroxy-coumarin and various benzaldehydes. Optimization studies were conducted regarding the most important reaction parameters such as reaction time, temperature and the molar ratio of reactants. It was ascertained that the reaction proceeded smoothly in 40oC in 3h, providing the desired 4-hydroxy-bis-coumarins in almost quantitative yields and high purity after simple aqueous work-up. The ILs could be recycled and re-used for three times without decrease in the yield. In addition, the physicochemical properties of the synthesized ILs were determined and their biodegradability level has been investigated applying the Biological Oxygen Demand (BOD-5) closed-bottle test. The first results indicated that the three ILs present satisfactory biodegradability potential, higher than 62%.