Nickel ferrite nanocrystalline as a green and recyclable catalyst for the synthesis of Spiro-oxindole-chromene

A separable NiFe2O4 nanocrystalline catalyst was synthesized via a simple co-precipitation method. The catalytic activity of this heterogenous catalyst was investigated to synthesize Spiro-oxindole-chromene derivates via Knoevenagel condensation, and Michael addition reaction under conventional heating condition. The catalyst showed a prominent catalytic activity in a good yield (86.74 %). This easily separated catalyst could be recycled efficiently for four cycles without significant loss of its activity. Furthermore, the products were investigated for the antioxidant activity using DPPH method. The IC50 of the compounds was found to be 182.3 ppm. The use of catalysts has been proven a simple, efficient and environmentally friendly reaction. Based on the results, it is known that the reaction could not be achieved without the presence of NiFe2O4 catalyst.