Straightforward heterogeneization of Cu(I) complexes of chiral pyridine containing macrocyclic ligands (Pc-L*) and their applications to cyclopropanation reactions

We have recently reported that copper(I) complexes of the new C1-symmetric pyridine-based 12 membered tetraaza macrocyclic (Pc-L*) ligands are competent catalysts in the enantioselective cyclopropanation of olefins employing ethyl diazoacetate (EDA) as carbene precursor.1 Heterogeneous single site catalysts in many cases show superior performances in terms of activity, selectivity and reciclability coupling together the advantages of heterogeneous and homogeneous systems.2 We report here preliminary results on the heterogeneization of our system. Cu(I) complexes (see fig), based on functionalised pyridine-containing macrocyclic chiral ligands were heterogeneized on mesoporous ordered and non-ordered silicas (Davisil, MCM-41, etc.) by the SHB method.2 Materials obtained were fully characterized for metal content, textural properties, hydrogen bonds between Cu complex and surface silanols by a pool of techniques. Catalysts were tested in enantioselective cyclopropanation of olefins and they showed performances at least comparable to those obtained with the homogeneous counterpart. Tests using both basic and ordered silicas with the aim of exploiting the confinement effect on stereoselectivity are currently in progress. References [1] Caselli, A.; Cesana, F.; Gallo, E.; Casati, N.; Macchi, P.; Sisti, M.; Celentano, G.; Cenini, S.. Dalton Trans. 2008, 4202. [2] C. Bianchini, P. Barbaro, V. Dal Santo, R. Gobetto, A. Meli, W. Oberhauser, R. Psaro, F. Vizza, Adv. Synth. Catal., 2001, 343, 41-45.