An environmentally benign aqueous protocol for the synthesis of novel 2-((5-(4-methoxybenzylidene)-4-oxo-4,5-dihydrothiazol-2-yl)amino)substituted acid by using potassium carbonate as a base has been achieved. These ultrasound irradiation and conventional technique reaction proceed efficiently in water in the absence of organic solvent. In comparison with conventional methods, our protocol is convenient and offers several advantages, such as shorter reaction time, higher yields, milder conditions and environmental friendliness.