“On water” highly atom economical and rapid synthesis of a novel class of 3-hydroxy-2-oxindole scaffolds under a catalyst-free and column chromatography-free protocol at room temperature

An “on water” highly atom economical and rapid protocol has been developed for the synthesis of a novel class of 3-(2-pyrazolin-5-one) substituted, 3-hydroxy-2-oxindole scaffolds under catalyst-free and column chromatography-free conditions at rt. The generality of the method has been demonstrated by screening a series of isatin electrophiles as well as 2-pyrazolin-5-one derivatives. The developed method is a good example of green synthesis in which straightforward synthesis of a medicinally important 3-hydroxy-2-oxindole framework is executed by employing very mild, simple and handy procedures from readily available starting materials.