One-pot, three-component synthesis of isoxazol-5(4H)ones using NH4H2PO4 in aqueous medium

The isoxazol-5(4H)one unit is found in many molecules, including naturally occurring bioactive compounds, pharmaceutical drugs, and agrichemicals. Derivatives of isoxazol-5(4H)ones are possess biological properties such as antibacterial, antiinflammatory,antifungal, anticancer, analgesic, anticonvulsive, anti-diabetic, antiandrogenic,hypoglycemic, inhibitory against PTP1B and the tumor necrosis factoralpha, herbicidal, and insecticidal activities [1]. Also, the isoxazol-5(4H)ones can be found in various synthetic intermediates for the synthesis of many heterocyclic compounds and other functional organic molecules [2]. It has long been known that the multicomponent reactions (MCRs) are powerful means of synthesizing high-value chemicals in a single reaction flask. Simpler procedures and equipment, time and energy savings, as well as environmental friendliness have all led to a sizable effort to design and implement MCRs in both academia and industry [3]. In this MCR, the use of ammonium dihydrogen phosphate catalyst allows cyclocondensation to be carried out in a single-step, three-component reaction of structurally diverse aldehydes with various β-oxo esters and hydroxylamine hydrochloride without isolation of intermediates to give the corresponding various isoxazol-5(4H)ones in aqueous medium at room temperature. The salient feature of this method includes mild conditions, relatively short reaction time, good to high yields, easy separation of products, and simple procedure.