Synthesis of 2-Aminothiophene Derivatives by Gewald Reaction Using Ultrasound Technique

Multicomponent reactions (MCRs) serve as powerful tools for the synthesis of a broad range of molecules and biologically active compounds due to the simplicity and efficiency associated with MCR protocols [1,2]. Despite many efforts devoted to develop the Gewald reaction, many procedures are not practically justified due to environmental and safety restrictions they impose. In addition, some of the methods are not economically feasible sincethey require long time heating at elevated temperatures; give low yields of products, and some other problems [3]. In this project, a facile and practical method has been developed for the preparation of 2- aminothiophene derivatives via the Gewald reaction by using ultrasound technique in a reasonably short period of time. Consequently, a series of 2-aminothiophenes were synthesized in high yields at room temperature. Under the conditions, several cyclic ketones react with malononitrile and sulfur to produce high yields of the respective products (Table 1).