Utilize este identificador para referenciar este registo: http://hdl.handle.net/10400.1/3229
Título: Supramolecular catalysis by cucurbit[7]uril and cyclodextrins: similarity and differences
Autor: Basilio, Nuno
García-Río, Luís
Moreira, José A.
Pessêgo, Márcia
Data: 2010
Editora: American Chemical Society
Citação: Basilio, Nuno; García-Río, Luís; Moreira, José A.; Pessêgo, Márcia. Supramolecular Catalysis by Cucurbit[7]uril and Cyclodextrins: Similarity and Differences, The Journal of Organic Chemistry, 75, 3, 848-855, 2010.
Resumo: To understand the analogies and differences between the cucurbituril and cyclodextrin cavities different solvolytic reactions have been studied in the presence of cucurbit[7]uril, CB7, and β-CD or its methylated derivative, DM-β-CD. Solvolysis of 1-bromoadamantane has been used as a test to evaluate the ability of the cavities to solvate the Br- leaving group. Obtained results show that in both cases the polarity inside the cavity is similar to that of a 70% ethanol:water mixture. Solvolysis of substituted benzoyl chlorides shows a great difference between the CB7 and DM-β-CD cavity. Solvolysis of electron withdrawing substituted benzoyl chlorides (associative mechanism) is catalyzed by DM-β-CD and inhibited by CB7. However, solvolysis of electron donating substituted benzoyl chlorides(dissociative mechanism) is catalyzed by CB7 and inhibited by DM-β-CD. These experimental behaviors have been explained on the basis of different solvolytic mechanisms. Participation of the hydroxyl groups of the cyclodextrin as a nucleophile can explain the catalytic effect observed for solvolysis of benzoyl chlorides reacting by an associative mechanism. Solvolysis of benzoyl chlorides reacting by a dissociative mechanism is catalyzed by CB7 due to the ability of the CB7 cavity to stabilize the acylium ion developed in the transition state by electrostatic interactions.
Peer review: yes
URI: http://hdl.handle.net/10400.1/3229
DOI: http://dx.doi.org/10.1021/jo902398z
ISSN: 0022-3263
Versão do Editor: http://pubs.acs.org/doi/pdf/10.1021/jo902398z
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