Unprecedented, catalyst-free, and rapid one-pot, three-component green synthesis of substituted 3-hydroxy-2-oxindoles in water

An efficient, unprecedented, catalyst-free, and rapid synthesis of substituted 3-hydroxy-2-oxindoles is described by the one-pot, three-component reaction of hydrazine hydrate, ethyl acetoacetate, and isatins in water. The reported protocol is a green and general route for the simple preparation of new heteroaromatic substituted 3-hydroxy-2-oxindoles in quantitative yields under very mild reaction conditions by using simple, cheap, and readily available materials. The developed method is effectively applicable to a variety of isatin substrates. Operational simplicity, mild and greener reaction conditions, short reaction time, a wide scope of substrates, good isolated yields of the products, and environmentally benign reaction medium are the distinctive features of the present method.