Synthesis of spiropyran derivatives over 1-(carboxymethyl) pyridinium iodide as nanostructured pyridinium salt under aqueous media

In this work, acetic acid functionalized pyridinium salt, namely 1(carboxymethyl) pyridinium iodide {[cmpy] I}, has been applied as reusable nanostructured catalyst for green, simple and efficient preparation of spiropyrans by the one-pot domino Knoevenagel-Michael-cyclization reaction of isatin derivatives or acenaphthenquinone, with malononitrile, and 1,3dicarbonyl compounds under aqueous media. Moreover, H-1 and C-13 NMR, mass, CHN analysis, Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), thermal gravimetric analysis (TGA), differential thermal gravimetric (DTG), X-ray diffraction analysis (XRD), and calculation of crystallite size and interplaner distance of the catalyst have been studied.