resumo
A copper C(2)-symmetric bis(oxazoline), CuBox, was introduced in two forms of commercial Y zeolite: a sodium form (NaY) and an ultrastable form (NaUSY). CuBox was introduced by first partially exchanging the sodium cations of both zeolites for copper and then by refluxing the obtained materials with a solution of bis(oxazoline) (Box). Two different loadings were prepared for each form of zeolite. The materials were characterized by copper ICP-AES, elemental analysis, XPS, FTIR, TG, and nitrogen adsorption isotherms at -196 degrees C. Evidence for Box ligand location in the supercages of NaY and NaUSY zeolites and its coordination to the exchanged copper(II) was obtained by the several techniques used. The materials were all active in the cyclopropanation of styrene with ethyldiazoacetate at room temperature and diastereoselective toward trans cydopropanes. Although the materials containing Box showed low enantioselectivities, their catalytic activities were higher than the parent copper exchanged zeolites, and did not decrease with reuse, at least during three consecutive cycles.
palavras-chave
ENANTIOSELECTIVE CATALYSIS; CHIRAL CATALYSTS; PILLARED CLAYS; COMPLEXES; EPOXIDATION; AZIRIDINATION; BISOXAZOLINES; OLEFINS
categoria
Engineering
autores
Silva, AR; Albuquerque, H; Fontes, A; Borges, S; Martins, A; Carvalho, AP; Pires, J
nossos autores
Ana Rosa Silva
Investigador PrincipalGrupos
agradecimentos
This work was funded by Fundacao para a Ciencia e a Tecnologia (FCT) through the project PTDC/QUI/64770/2006, which was cofinanced by EU under the programs COMPETE, QREN, and FEDER. A.R.S. thanks FCT, FSE, and POPH for the contract under the program Ciencia 2008.