The immobilization of chiral catalysts on and inside dendrimers

Chiral dendrimer catalysts, which possess a high level of structural regularity, molecular monodispersity and well-defined catalytic sites, have been generated either by attachment of achiral complexes to chiral dendrimer structures or by immobilisation of chiral catalysts to the established non-chiral dendrimers. As monodipersed macromolecular supports they provide ideal model systems for less regularly structured but commercially more viable supports such as hyperbranched polymers and have been successfully employed in continuous-flow membrane reactors. Since enantioselection in a stoichiometric or catalytic reaction is governed by small increments of free enthalpy of activation such transformations are in principal particularly suited to assess ‘dendrimer effects’ that result from catalyst immobilization. More elaborate further developments such as the use of dendritic catalysts in biphasic solvent systems have only just begun and appear to provide fruitful fields for further development.