Ultrasound mediated green synthesis of rhodanine derivatives: Synthesis, chemical behavior, and antibacterial activity

A variety of rhodanine derivatives were synthesized via a three-component reaction of carbon disulfide, amines, and dialkyl acetylenedicarboxylate in polyethylene glycol under conventional stirring or ultrasound irradiation. The sonochemical-assisted procedure provides an improved and accelerated conversion when compared to the conventional reaction, with increased rate of reaction and quality of product obtained. The product formed, 2a, could be readily converted to bis-rhodanine under microwave conditions. Moreover, the pyranothiazoles 9a,b were prepared from the corresponding rhodanines 2a,b and malononitrile. Fifteen compounds were screened for their antibacterial activities against nine human, animal and plant pathogenic Gram-positive and Gram-negative bacteria using the agar well diffusion method. Out of these derivatives, compounds 2g and 2h were the most effective against all tested bacteria.