An improved protocol for the synthesis of 3,4-disubstituted isoxazol-5(4H)-ones through L-valine-mediated domino three-component strategy

An expeditious, metal-free protocol has been demonstrated for the synthesis of isoxazolone derivatives using domino multi-component strategy. The envisaged methodology involves the L-valine promoted three-component cyclo-condensation reaction of alkylacetoacetates, hydroxylamine hydrochloride and aldehydes in ethanol under reflux. The reaction proceeded to deliver the desired products in good to excellent yields (74–97%), exhibited good functional group tolerance and completed in less than 4 min with most of the substrates. High yields, short reaction time, noncorrosive organocatalyst, mild reaction conditions, clean reaction profiles and the absence of any tedious workup or purification are the beneficial features of this process. Moreover, quantum computational study has been performed at B3LYP/6-311G++(d, p) level to investigate the various DFT based molecular descriptors, HOMO–LUMO energy gap and electrostatic potential surface properties of the synthesized product.

Graphic abstract

An improved protocol for the synthesis of 3,4-disubstituted isoxazol-5(4H)-ones through L-valine-mediated domino three-component strategy