Ionic Liquid Based Organosilica Modified with Sulfonic Acid: As a Novel and Reusable Catalyst for the Biginelli Reaction

In this study, a novel and effective sulfonic acid containing organosilica with ionic liquid framework (OIL@SO3H) catalyst is prepared, characterized and its performance is developed in the synthesis of Biginelli products under moderate conditions. The OIL@SO3H material was prepared by simultaneous hydrolysis and condensation of 1,3-bis(3-trimethoxysilylpropyl)-imidazolium iodide and 3-thiopropyltrimethoxysilane followed by treatment with hydrogen peroxide. The OIL@SO3H catalyst was characterized using several techniques such as Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) , thermal gravimetric analysis (TGA), powder X-ray diffraction (XRD) and energy dispersive X-ray (EDX) analyses. This catalyst was successfully used in the one pot Biginelli condensation of aldehydes with urea and alkyl acetoacetates and delivered corresponding products in high to excellent yields and selectivity under solvent free media. Moreover, the recoverability and reusability of the catalyst were also studied under applied reaction conditions. The result showed that the designed catalyst could be recovered and reused at least four times without significant decrease in stability and efficiency.