The indole framework has been identified as one of the most important pharmacophore present in a wide array of bioactive compounds (both natural and synthetic) including several drugs. An operationally simple, ultrasound-assisted clean procedure for the synthesis of 3,3-di(3-indolyl)-2-oxindoles and 3-indolyl-3-hydroxy oxindoles has been developed using catalytic amount of ecofriendly Lewis acid in aqueous medium. The present economical method satisfies most of the principles of green chemistry such as: cost effectiveness, low toxicity, air and moisture sensitivity as well as the use of green aqueous medium. The procedure is equally effective for differently substituted indoles and isatins. The excellent yield of the products within shorter reaction time make this methodology a valid contribution to the existing processes in the same field. This procedure tolerates a relatively wide range of substrates and excellent results are obtained for gram-scale reactions “on water”, which opens up a new pathway to various biologically significant substituted oxindoles through one-pot route. A plausible mechanistic pathway has also been suggested.

Ultrasound-assisted green synthesis of diversely substituted oxindoles

249th National Meeting (2015)

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