Hydroxyl Functionalized Lewis Acidic Ionic Liquid on Silica: An Efficient Catalyst for the C-3 Friedel-Crafts Benzylation of Indoles with Benzyl Alcohols

In this work, a hydroxyl functionalized Lewis acidic ionic liquid on silica is found to be an efficient heterogeneous catalyst for the C-3 Friedel-Crafts benzylation of indoles with different benzyl alcohols as benzylation agents under mild conditions. This catalytic system benefits from simple operation, work-up and reutilization procedures, wide substrate tolerance, low cost, high catalytic activity and excellent chemo-selectivity. The hybrid combination of hydroxyl functionalized ionic liquid and silica through the formation of hydrogen bond endows this catalyst with high stability in the Friedel-Crafts reaction system, and the catalyst could be easily recycled and reutilized. Graphical Abstract A hydroxyl functionalized Lewis acid ionic liquid supported on silica was found to be an efficient catalyst for the C-3 Friedel-Crafts benzylation reaction of iodole with alcohols. This catalyst benefits from low cost, feasible preparation and reutilization, high catalytic activity and selectivity, and the operation and work-up procedures are very simple. [GRAPHICS] .