Efficient Synthesis of 4-Arylmethylene-3-methylisoxazol-5(4H)-one Derivatives Catalyzed by Malic Acid

The efficient, straightforward, and green procedure was established in the direction of synthesis of 4-arylmethylene-3-methylisoxazol-5(4H)-one derivatives using the malic acid, which acted as the catalyst for the three-component heterocyclization reaction. In this reaction, aryl/heteroaryl aldehydes, hydroxylamine hydrochloride, and ethyl acetoacetate/ethyl benzoylacetate were applied as the reactants. The reaction was optimized to attain the best conditions for the synthesis of target heterocyclic compounds in a single step route. The best results were obtained from optimization experiments using 10 mol% malic acid as the catalyst, water solvent, and 50ºC temperature. The noticeable features of this process are the simplicity of the experimental procedure, the easy separation of the pure compounds from the product mixture, the simplicity of operation, avoidance of any hazardous organic solvents, no use of chromatographic purification techniques, clean reaction profiles, high yields, relatively short reaction time, and eco-friendliness.