BMIm[OH] Catalyzed Rapid, Mild and Improved Protocol for the Synthesis of 3-Hydroxy-3-(nitroalkyl)indolin-2-one Derivatives in Water

A sustainable route for the Henry reaction of isatins with nitromethane or nitroethane to afford 3-hydroxy-3-(nitroalkyl)indolin-2-ones was developed by the catalysis of 1-butyl-3-methyl imidazolium hydroxide (BMIm[OH]) ionic liquid in water-SDS system. Incorporation of SDS in the reaction medium enhances the reaction rate by suppressing the solubility issues for different substrates particularly for N-alkylated isatins. This method provides high yield of the condensation product in a shorter reaction time under a very mild condition and in a multi-gram scale reaction. Moreover, recyclability of the catalyst ionic liquid as well as reaction medium including surfactant makes the present protocol environmentally benign.