Cross‐linked poly(<i>N</i>‐vinylpyrrolidone)‐titanium tetrachloride complex: A novel stable solid TiCl<sub>4</sub> equivalent as a recyclable polymeric Lewis acid catalyst for regioselective ring‐opening alcoholysis of epoxides
Ali Rahmatpour, Seyed Mehrzad Sajjadinezhad
Abstract
Abstract Cross‐linked poly( N ‐vinylpyrrolidone) resin beads were prepared as macromolecular ligand precursors by suspension copolymerization of N ‐vinyl‐2‐pyrrolidone and N , N ′‐methylenebisacrylamide (MBA) as a crosslinking agent in water. Subsequently, the resulting polymer carrier precursor was readily combined with titanium tetrachloride to form a stable polymeric coordination complex (PNVP/TiCl 4 ), and this novel stable TiCl 4 equivalent evaluated as a heterogeneous and reusable solid Lewis acid catalyst for the regio‐and stereoselective nucleophilic ring opening of various epoxides with various alcohols to prepare β ‐alkoxy alcohols in excellent yields without generating any waste. The MBA‐cross‐linked PNVP and resultant catalyst were characterized by Fourier transform infrared spectroscopy (FT–IR), field‐emission scanning electron microscope (FE–SEM), energy dispersive X‐ray (EDX), inductively coupled plasma (ICP), and thermogravimetric analysis (TGA) techniques. Moreover, the catalyst is very stable, easily separated, and reused at least five times without significant loss of activity. In terms of scope, yields, the amount of catalyst used, and reaction time, the PNVP‐TiCl 4 complex catalyst is an improvement over previously reported heterogeneous catalysts for ring opening of epoxides methods. Further, the experimental outcome revealed that using the copolymer beads as carriers with a high percentage of crosslinking and the high mesh size leads had an adverse effect on the reaction rate.