Triphenylphosphane: An Efficient Catalyst for Three-Component Synthesis of Arylmethylidene-isoxazole-5(4H)-ones in Green Medium

Heterocycles are obtaining more importance in recent years due to their pharmacological activities.The isoxazole core is a significant synthetic line of attack in drug discovery, and playsa significant role in arena of natural products, agrochemicals, and medicinal chemistry [1].Compounds containing this scaffold exhibit versatile biological properties such as antibacterial,anti-obesity, anti-inflammatory, antifungal, analgesic, and fungicidal activities [2]. Conventionalmethods for the synthesis of arylmethylidene-isoxazole-5(4H)-ones are the cyclizationof O-propioloyl oximes, the reaction of ethyl acetoacetate and hydroxylamine hydrochloridefollowed condensation with aromatic aldehydes, and condensation of 1,3-dicarbonylswith benzaldoximes. Significant development has been made in reviewing different routes forthe construction of an arylmethylidene-isoxazole-5(4H)-one skeleton [2-3]. A highly yieldingapproach for the synthesis of arylmethylidene-isoxazole-5(4H)-ones has been established usingtiphenylphosphane as the efficient catalyst. Here, the three-component reaction of ethylacetoacetate, various aromatic aldehydes, and hydroxylamine hydrochloride, under aqueousconditions at room temperature is described. This procedure has expectant features, includingshorter reaction times, easy separation of pure products with high yields, simplicity experimentalprocedure, operationally simple, and eco-friendly.