Recent developments of heterogeneous solid catalysts for liquid-phase Friedel-Crafts type benzylation reaction

Liquid-phase Friedel-Crafts type benzylation of aromatics has been effected traditionally with catalysis by homogeneous protonic acid or Lewis acid. However, heterogeneous catalysts have the advantages, compared to their homogeneous counterparts, of facile recovering and recycling. This short article describes the recent advances in the liquid-phase Friedel-Crafts type benzylation by benzyl chloride of aromatics over redox metal: gallium (Ga), indium (In) and thallium (Tl) containing novel heterogeneous solid Catalysts. Unlike conventional acidic catalyst. the benzylation activity of the Ga-, In- or Tl-based solids does not depend solely on their acidic properties, even present. these solids in their non-acidic or basic form also shows high benzylation activity. The catalytic activity order of Ga. In and Tl containing solid catalysts Supported on chemically similar inert catalyst carrier is as follows: thallium/support > indium/support > gallium/support, Which is quite similar to their redox potential values indicating the role of redox function in the benzylation process. A plausible reaction mechanism for the benzylation reaction over these catalysts is proposed. These heterogeneous solids are highly efficient for the Friedel-Crafts type benzylation, even in the presence of moisture. than the conventional strongly acidic solid acid catalysts.