Water versus solvent-free conditions for the enantioselective inter- and intramolecular aldol reaction employing L-prolinamides and L-prolinethioamides as organocatalysts

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Título: Water versus solvent-free conditions for the enantioselective inter- and intramolecular aldol reaction employing L-prolinamides and L-prolinethioamides as organocatalysts
Autor/es: Almasi, Diana | Alonso, Diego A. | Balaguer Alba, Andrea-Nekane | Nájera, Carmen
Grupo/s de investigación o GITE: Procesos Catalíticos en Síntesis Orgánica
Centro, Departamento o Servicio: Universidad de Alicante. Departamento de Química Orgánica
Palabras clave: Aldol reaction | Asymmetric organocatalysis | Prolinethioamides | Solvent-free reaction | Water
Área/s de conocimiento: Química Orgánica
Fecha de creación: 3-feb-2009
Fecha de publicación: 12-may-2009
Editor: Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Cita bibliográfica: ALMASI, Diana, et al. "Water versus solvent-free conditions for the enantioselective inter- and intramolecular aldol reaction employing L-prolinamides and L-prolinethioamides as organocatalysts". Advanced Synthesis & Catalysis. Vol. 351, Issues 7-8 (May 2009). ISSN 1615-4150, pp. 1123-1131
Resumen: Organocatalysts 1, derived from L-proline and (1S,2R)-cis-1-aminoindan-2-ol or (R)-1-aminoindane, are evaluated as promoters in the direct asymmetric aldol reaction between ketones and aromatic aldehydes in the presence of water and under solvent-free reaction conditions. L-Prolinethioamides 1c and 1d exhibited higher enantioselectivity than the corresponding prolinamides 1a and 1b in the model aldol reaction between cyclohexanone and 4-nitrobenzaldehyde in the presence of 4-nitrobenzoic acid as cocatalyst. In particular, L-prolinethioamide 1d (5 mol%), derived from L-proline and (R)-1-aminoindane, is shown as the most efficient organocatalyst studied promoting the direct aldol reaction of cycloalkyl, alkyl, and α-functionalized ketones with aromatic aldehydes in the presence of water and under solvent-free reaction conditions employing only 2 equivalents of nucleophile. Generally, anti-aldol products are obtained in high yields and excellent diastereo- and enantioselectivities (up to >98/2 anti/syn, up to 98% ee). Solvent-free conditions give slightly higher dr and ee than using water as solvent. In addition, organocatalyst 1d can be easily recovered by extractive work-up and reused. Prolinethioamide 1d (5 mol%) in combination with 4-NO2C6H4CO2H (5 mol%) is also a very effective organocatalytic system for the asymmetric solvent-free intramolecular Hajos-Parrish-Eder-Sauer-Wiechert reaction with comparable or higher levels of enantioselectivity (up to 88% ee) to other reported catalysts in organic solvents.
Patrocinador/es: Financial support from the MEC (Projects CTQ2004-00808/BQU, CTQ2007–62771/BQU and Consolider INGENIO 2010 CSD2007-00006), from the Generalitat Valenciana (GRUPOS05/11, GV05/144, GV/2007/142) and the University of Alicante.
URI: http://hdl.handle.net/10045/10888
ISSN: 1615-4150 (Print) | 1615-4169 (Online)
DOI: 10.1002/adsc.200800814
Idioma: eng
Tipo: info:eu-repo/semantics/article
Derechos: The definitive version is available at www3.interscience.wiley.com
Revisión científica: si
Versión del editor: http://dx.doi.org/10.1002/adsc.200800814
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