abstract
A copper(II) complex with a commercial chiral bis(oxazoline) was anchored onto ordered mesoporous silica materials and their respective carbon replicas. The amount of transition metal complex loaded onto the mesostructured solids was determined by ICP-AES and the materials were also characterized by elemental analysis, FTIR, TG/DSC and isotherms of N-2 adsorption at -196 degrees C. For the first time the asymmetric benzoylation of a 1,2-diol was performed in the heterogeneous phase by using an anchored commercial bis(oxazoline) ligand. The effect of the type of mesoporous material on the catalytic parameters, as well as on the reutilization of catalysts in several catalytic cycles, was checked. All the composites prepared were active, selective and enantioselective in this asymmetric organic transformation. Using the two ordered mesoporous silicas as supports good selectivities, with comparable yields and TONs to the homogeneous phase reaction, were obtained. Furthermore these two heterogeneous catalysts are more stable upon reuse than the corresponding ordered carbon replica materials. One of the former heterogeneous catalysts, with mesoporous silica as a support, could be further reused for 4 consecutive cycles without significant loss of selectivity, the TON or enantioselectivity.
keywords
FUNCTIONALIZED ACTIVATED CARBONS; ENANTIOSELECTIVE CATALYSIS; HETEROGENEOUS CATALYSTS; KINETIC RESOLUTION; CHIRAL CATALYSTS; COMPLEXES; LIGANDS; IMMOBILIZATION; EPOXIDATION; ACETYLACETONATE
subject category
Chemistry
authors
Silva, AR; Carneiro, L; Carvalho, AP; Pires, J
our authors
Ana Rosa Silva
Principal ResearcherGroups
Projects
acknowledgements
This work was funded by Fundacao para a Ciencia e a Tecnologia (FCT) through the project PTDC/QUI/64770/2006, which was co-financed by EU under the programs COMPETE, QREN and FEDER. ARS thanks FCT, FSE and POPH for the contracts under the programs Ciencia 2008 and Investigator FCT 2012, as well as for financing under the program Pest-C/CTM/LA0011/2011 (CICECO) and PEst-OE/QUI/UI0612/2013 (CQB/FC/UL). We would also like to acknowledge Dr Monica Valega and Prof. Fernando Domingues from the Department of Chemistry of the University of Aveiro for the initial help in the HPLC analytical method development.