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A green, efficient, rapid, high-yielding, catalyst-free method for the synthesis of rhodanines in water using ultrasonic irradiation is described. The procedure is straightforward and the rhodanine products are isolated by simple filtration.The use of water as a solvent has many advantages in organic processes and reactions, both in industry and in green chemistry applications. It is economical, non-toxic and environmentally friendly. The hydrophobic products produced when using water as the solvent are separable by extraction with an organic solvent. 1 Increasingly, ultrasound has been used in organic synthesis. 2 Compared with traditional methods, the use of ultrasound is more convenient and easily controlled. A large number of organic reactions can be carried out in higher yields and shorter times under mild ultrasonic irradiation conditions. [2][3][4][5] One of the main objectives of organic and medicinal chemistry is the design and synthesis of molecules having value as human therapeutic agents. 6 Rhodanines, in particular, are known to possess a wide spectrum of biological activity including the inhibition of targets such as HCV NS3 protease 6 and b-lactamase. 7 As a part of our ongoing research on the synthesis of heterocyclic compounds with medicinal applications, 8 and based on our previous study on the synthesis of rhodanine, 9 we became interested in the development of a green and practical method to synthesize rhodanines of potential pharmacological and biological interest via sonochemistry.Herein, we report a simple, efficient, one-pot method for the synthesis of rhodanine derivatives in high yields (86-94%) and in short times (3-5 minutes) using ultrasonic irradiation and water as the reaction medium.In order to evaluate the efficiency of this method the synthesis of rhodanine 3a, via reaction of dimethyl acetylenedicarboxylate (DMAD, 2a), carbon disulfide (CS 2 ) and benzylamine (1a) as a model system, was carried out in water using ultrasonic irradiation (US) or high-speed stirring (HSS) ( Table 1).To our surprise, the one-pot, three-component synthesis of rhodanine 3a in water as the solvent using ultrasonic irradiation was complete in three minutes, but the highspeed stirring method required a reaction time of one hour to go to completion (Figure 1). We next investigated the effect of various solvents on the synthesis of rhodanine 3a (model system) using ultrasonic irradiation and high-speed stirring. In each case reactions using the ultrasound method were complete within three minutes with the highest yield of 94% being obtained in Table

Uniform and small particle size of palladium was generated onto the SH-decorated SBA-15 pore-walls.

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