Polyethylene glycol (PEG-200)-promoted sustainable one-pot three-component synthesis of 3-indole derivatives in water

A sustainable three-component reaction of indoles, aldehydes, and malononitrile in water promoted by polyethylene glycol (PEG-200) afforded 3-indole derivatives in good to excellent yields.

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► A sustainable protocol for synthesis of 3-indole derivatives was established.
► Reaction of indoles, aldehydes, malononitrile was promoted by PEG-200 in water.
► The metal catalysts such as copper or indium are not required in this protocol.
► The reaction media can be reused four times without erosion of the yield.
► The target products often can be easily isolated by simple filtration.