Proline-modified poly(propyleneimine) dendrimers as catalysts for asymmetric aldol reactions

A series of surface-functionalized poly(propyleneimine) dendrimers (five generations) based on proline were synthesized and were evaluated as catalysts for asymmetric aldol reactions. Using 6.5 mol% of the second generation modified dendrimer as catalyst, the products of the aldol reactions were obtained in yields and and ee's comparable to those observed using proline itself, in much less reaction time (2 h) in comparison to that required for proline (16-18 h). In addition, the improved solubility of dendritic catalysts in organic solvents provides completely homogeneous reaction mixtures.