Heterogeneous Organic Reactions In Aqueous Media Promoted By Combined Ultrasound-Microwave Irradiation

Using aqueous media to perform organic synthesis reactions can eliminate or mostly diminish the employment of organic solvent. However, organic reactions in water usually become heterogeneous systems due to the hydrophobic characters of organic reagents. Intensification of process in heterogeneous reactions has been considered much important for this "green chemistry" strategy. By utilizing the combined energy irradiation with ultrasound and microwave as a tool of intensification, we present herein the high-speed synthesis of 9 2-amino-5-aryl-[1,3,4]-thiadiazoles and 8 compounds of amino-thiadiazole Schiff base in aqueous media, while the yields and purities of products are satisfactory. In these cases, the synergy effect of combined energy irradiation is observed to be more efficient than the sum of single energy irradiation. The mechanism of intensification in solid-liquid heterogeneous reactions by simultaneously ultrasound and microwave irradiation has also been probed. The eroding degree of the surface of solid particles in water under different energy irradiation has been compared to demonstrate the removal of passivation coat on the substrate particles in solid-liquid reaction system, which is the reason of remarkable intensification by combined energy irradiation to this kind of system.