Silica-supported Policresulen As A Solid Acid Catalyst For Organic Reactions

With increasing pressure coming from environment protection, it appealingly needs to develop green synthetic systems with environmentally benign acid catalysts. The use of heterogeneous solid acid catalysts assumes generally advantages like ease of operation conditions, reduced equipment corrosion, and minimized contamination of the waste streams combined with reusability of the catalyst. For this reason, heterogeneous solid acids have been extensively investigated, and in some chemical processes, their utilizations have already contributed to significant improvement on both of the synthetic efficiency and the greenness of the system.A new type solid catalyst was prepared by coating a thin layer of policresulen, which is an inexpensive polymer prepared via condensation of 2-hydroxy-4-methylbenzenesulfonic acid and formaldehyde and has been used as a commercially available drug, onto the surface of silica. The Policresulen component is insoluble in many organic solvents and can be absorbed on silica with the aid of hydrogen bonding. The obtained silica/policresulen composite showed remarkable catalytic activities for various organic reactions. In representative reactions, this catalyst can be recycled for several times without significant loss of activity.The salient features of using this acid catalyst in organic reactions include cost-effectiveness, simple and time-efficient preparation, and easily controllable loading on the solid.