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Alicante, Spain

Guillena G.,Institute Sintesis Organica | Ramon D.J.,Institute Sintesis Organica | Yus M.,Institute Sintesis Organica
Chemical Reviews | Year: 2010

The versatility and usefulness of heterogeneous and homogeneous catalysts in the alkylation of amines through the so-called hydrogen autotransfer process was reviewed. Mechanistic studies on the homogeneous iridium-catalyzed alkylation of amines with alcohols have been performed using density functional theory (DFT) calculations. This study showed that the found reaction energetic barriers were consistent with the experimental requirements of elevated temperatures. The first alkylation of amines through an indirect aza-Wittig process was performed using the former iridium source. A similar complex has been used in the alkylation of primary amines with primary and secondary alcohols to give a mixture of products. The use of this strategy of alkylation substitutes the classical ones employing hazardous and expensive alkyl halides, sulfonates, or sulfates and allows a greener process, since the only generated waste is water or ammonia. Moreover, the low molecular weight of wastes makes this synthetic strategy unbeatable as far as the atom efficiency numbers are concerned.

Banon-Caballero A.,Institute Sintesis Organica | Guillena G.,Institute Sintesis Organica | Najera C.,Institute Sintesis Organica | Faggi E.,Autonomous University of Barcelona | And 2 more authors.
Tetrahedron | Year: 2013

Silica-gel supported binam-derived prolinamides are efficient organocatalysts for the direct intramolecular and intermolecular aldol reaction under solvent-free conditions using conventional magnetic stirring. These organocatalysts in combination with benzoic acid showed similar results to those obtained under similar homogeneous reaction conditions using an organocatalyst of related structure. For the intermolecular process, the aldol products were obtained at room temperature and using only 2 equiv of the ketone with high yields, regio-, diastereo- and enantioselectivities. Under these reaction conditions, also the cross aldol reaction between aldehydes is possible. The recovered catalyst can be reused up to nine times providing similar results. More interestingly, these heterogeneous organocatalysts can be used in the intramolecular aldol reaction allowing the synthesis of the Wieland-Miescher and ketone analogues with up to 92% ee, with its reused being possible up to five times without detrimental on the obtained results. © 2012 Elsevier Ltd. All rights reserved.

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