Efficient four‐component synthesis of spiroindole derivatives catalysed by a versatile and reusable nano‐paramagnetic catalyst

A simple, efficient and environmentally benign route was developed for the preparation of spiro(indoline‐3,4‐pyrano[2,3‐c]pyrazole) derivatives with good yields from condensation of isatins, malononitrile (or ethyl cyanoacetate), hydrazine hydrate and ethyl acetoacetate catalysed by PFu@Fe3O4 nanocomposite. The use of easily available catalyst, shorter reaction times, better yields, simplicity of reaction, heterogeneous system and easy work‐up are the advantages of the method presented. Characterization of the catalyst was performed using Fourier transform infrared spectroscopy, X‐ray diffraction and transmission electron microscopy. Spiro [indoline‐3,4‐pyrano [2,3‐c]pyrazole] derivatives were synthesized by four‐component condensation of isatin, malononitrile, ethyl acetoacetate and hydrazine using nano PFu@Fe3O4 in excellent yields. This new nano‐paramagnetic reagent is an easily separable, reusable, safe and green heterogeneous catalyst.