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Browsing by Author "Antunes, Margarida M."

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  • A hydrogen-bonded assembly of cucurbit[6]uril and [MoO2Cl2(H2O)(2)] with catalytic efficacy for the one-pot conversion of olefins to alkoxy products
    Publication . Nogueira, Lucie S.; Antunes, Margarida M.; Gomes, Ana C.; Cunha-Silva, Luis; Pillinger, Martyn; Lopes, Andre D.; Valente, Anabela A.; Goncalves, Isabel S.
    The reaction of the macrocyclic cavitand cucurbit[6]uril (CB[6]) and the diaqua complex [MoO2Cl2(H2O)(2)] in hydrochloric acid solution gave a water insoluble supramolecular compound with the general composition 2[MoO2Cl2(H2O)(2)]center dot CB[6]center dot xH(2)O center dot yHCl center dot z(CH3COCH3) (2). Single crystal X-ray diffraction (XRD) analysis revealed the presence of barrel-shape supramolecular entities, {CB[6]center dot 10(H2O)}, aligned in layers which are shifted relative to adjacent layers to form a brick-like pattern. The CB[6]/water hydrogen-bonded entities further engage in intermolecular interactions with water, HCl and [MoO2Cl2(H2O)(2)] molecules to form a three-dimensional (3D) framework. Compound 2 was characterised by thermogravimetric analysis (TGA), IR and Raman vibrational spectroscopy, and C-13{H-1} CP MAS NMR. The reference complex [MoO2Cl2(H2O)(2)]center dot(diglyme)(2) (1) and compound 2 were studied for the oxidative catalytic conversion of olefins (cis-cyclooctene, cyclohexene and styrene) with aqueous H2O2 as oxidant. Using alcohols as solvents, 2 was employed in a one-pot two-stage strategy for converting olefins to alkoxy products, which involves oxidation (with H2O2) and acid chemistry. Mechanistic studies were carried out using different intermediates as substrates, and the type of solvent and substrate scope were investigated. The results demonstrated the ability of the CB[6]/Mo-VI supramolecular adduct to function as an acid-oxidation multifunctional catalyst, and its recovery and reuse via relatively simple procedures.
    2019-08Journal article Restricted Show more
  • Catalytic alcoholysis of epoxides using metal-free cucurbituril-based solids
    Publication . Bruno, Sofia M.; Gomes, Ana C.; Oliveira, Tânia S. M.; Antunes, Margarida M.; Lopes, Andre D.; Valente, Anabela A.; Gonçalves, Isabel S.; Pillinger, Martyn
    Metal-free cucurbit[7]uril (CB7) solid-state assemblies promote acid-catalysed alcoholysis of aliphatic and aromatic epoxides under mild conditions to give beta-alkoxy alcohols, which are important intermediates for the synthesis of a vast range of compounds such as bioactive pharmaceuticals. The catalytic process is heterogeneous and the catalyst can be reused in consecutive runs without any reactivation treatment. The acid species responsible for the catalytic activity of CB7 may be entrapped hydronium ions.
    2016Journal article Restricted Show more