3‐Pyrazolyl‐oxindoles as efficient nucleophiles for construction of 3,3′‐diheterocycle substituted oxindoles using chitosan as reusable catalyst in water

A facile, one‐pot, environmentally benign and chitosan‐catalyzed protocol for the construction of a novel 3,3′‐diheterocycle substituted oxindole framework by three‐component reaction between 3‐pyrazolyl‐oxindoles, salicylaldehydes, and malononitrile in water is reported. This protocol provides several advantages including readily available starting materials, a simple operation, without the need of purification by column chromatography, reusable catalyst.