Switchable Perfomance of an l-Proline-Derived Basic Catalyst Controlled by Supramolecular Gelation
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Scholar |
Otros documentos de la autoría: Rodríguez Llansola, Francisco; Escuder, Beatriu; Miravet, Juan
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http://dx.doi.org/10.1021/ja902589f |
Metadatos
Título
Switchable Perfomance of an l-Proline-Derived Basic Catalyst Controlled by Supramolecular GelationFecha de publicación
2009Editor
American Chemical SocietyISSN
0002-7863Tipo de documento
info:eu-repo/semantics/articleVersión de la editorial
http://pubs.acs.org/doi/abs/10.1021/ja902589fPalabras clave / Materias
Resumen
An l-proline-derived low molecular weight gelator forms gels in nitromethane and nitroethane and acts as a basic catalyst for the Henry nitroaldol reaction of these solvents with 4-nitrobenzaldehyde and 4-chlorobenz ... [+]
An l-proline-derived low molecular weight gelator forms gels in nitromethane and nitroethane and acts as a basic catalyst for the Henry nitroaldol reaction of these solvents with 4-nitrobenzaldehyde and 4-chlorobenzaldehyde. The reported catalyst is efficient only upon aggregation into self-assembled fibrillar networks. The formation of the gels is associated to a basicity boost of the l-proline residues. Gel dissociation blocks the catalytic efficiency for the nitroaldol reaction but enhances a reaction pathway leading to alkenes. Because of the reversible nature of supramolecular gels, subtle temperature changes allow for a reversible sol−gel transition associated to an activation of the catalyst. The catalytic gel from nitroethane is significantly more active than the one from nitromethane probably because of its different structure as revealed by X-ray diffraction and thermal stability studies. The results shown indicate that in solution the l-proline moiety catalyzes the reaction of nitroalkanes with aldehydes via iminium intermediates while efficient nitroaldol reactions are promoted in the gel phase through an ionic pair type mechanism. The fact that upon aggregation the amino acid-based molecule used as gelator plays both a structural (gel formation) and catalytic role is interesting for the point of view of life origin studies. [-]
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Journal of the American Chemical Society, 131, 32, p. 11478–11484Derechos de acceso
Copyright © 2009 American Chemical Society
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