New eco-friendly procedure for the synthesis of 4-arylmethylene-isoxazol-5(4<i>H</i>)-ones catalyzed by pyridinium <i>p</i>-toluenesulfonate (PPTS) in aqueous medium

<p>In this work we describe a new, highly efficient method for the synthesis of 3-methyl-4-arylmethylidene-isoxazol-5(4H)-one derivatives by a three-component reaction between aromatic aldehydes, ethyl acetoacetate, and hydroxylamine hydrochloride under the influence by PPTS as a low-toxicity, inexpensive, commercially available and easy to handle catalyst. The advantages of this procedure are good yields, short reaction times, simplicity of implementation, and respect of the environment.