Green and three-component synthesis of isoxazolones using natural sunlight and investigating their antibacterial activity

The green and efficient three-component reaction between aromatic and heteroaromatic aldehydes, β-ketoesters (ethyl acetoacetate and ethyl benzoylacetate) and hydroxylamine hydrochloride in water and under natural sunlight leads to the formation of various derivatives of 4-arylidene-isoxazole-5(4H)-ones. In this reaction, natural sunlight was used outdoors as a green, cheap, clean, available, safe and non-toxic source of energy. The reactions were carried out in Damghan under sunlight. In this synthetic method using sunlight, the heterocyclization reaction was performed with simple tools and without the use of special equipment. In this three-component reaction, 4-arylidene-isoxazole-5(4H)-ones were synthesized in a range of 17-40 minutes and with yields ranging from 89-97%. The advantages of this suitable and green method can be mentioned abundant sunlight or low-energy visible light as an energy source, no environmental pollution, very mild reaction conditions, simplicity of the reaction method, easy separation, no use of organic solvents and catalysts. Some compounds were tested for antibacterial activity using Staphylococcus aureus and Escherichia coli by disk diffusion method. Some synthesized compounds have good antibacterial activity. The antibacterial activity of synthesized heterocycles is higher against Escherichia coli.