Application of dendronized-metal complexes on silica as catalysts for organic synthesis

Abstract

This thesis describes a variety of synthetic attempts to prepare dendrimer-metal complexes anchored to silica. The new complexes were obtained by immobilization of a tridentate diphosphinoaryl ligand (PCP-type) palladium(II) complex onto silica and silica supported dendrimers which combine the advantages of heterogeneous and homogeneous catalysts. They are thermally stable and they are also stable towards oxygen and moisture. These complexes show high catalytic activity for the Heck reaction of aryl iodides with styrene and n-butyl acrylate, resulting in high yields of stilbene and cinnamate ester. They are also active in the reactions of a variety of aryl bromides with n-butyl and methyl acrylate, providing para-substituted cinnamate esters in good yields. These complexes are also effective catalysts for the cyclocarbonylation reaction of 2-allylphenol yielding five- or seven-membered ring lactones in good selectivity and in high yields. In addition, these complexes can be recycled by simple filtration in air and reused with little to moderate loss of activity. In both kinds of reactions, the dendritic systems show higher activity compared to the non-dendritic systems.