Noncovalently functionalized dendrimers as recyclable catalysts

The efficient reversible functionalization of the periphery of urea adamant yl poly(propylene imine) dendrimers with catalytic sites using noncovalent interactions is described. Phosphine ligands equipped with urea acetic grou ps, a binding motive complementary to that of the dendrimer host, have been prepared and assembled to the dendrimer support. The resulting supramolecu lar complex has been used as a multidentate ligand system in the palladium- catalyzed allylic amination reaction in a batch process and in a continuous -flow membrane reactor. We found that the activity and selectivity of the d endrimeric complex is similar to that of the monomer complex, which indicat es that the catalytic centers act as independent sites. The size of the sup ramolecular system is sufficiently large and the binding of the guests is s trong enabling a good separation of the catalyst components from the reacti on mixture using nanofiltration techniques.