Highlights of Transition Metal-Catalyzed Asymmetric Hydrogenation of Imines

• Published in: ChemCatChem 2010-11, Vol.2 (11), p.1346-1371
• Main Authors: Fleury-Brégeot, Nicolas, de la Fuente, Verónica, Castillón, Sergio, Claver, Carmen
• Format: Article
• Language: English
• Subjects: asymmetric catalysis; homogeneous catalysis; hydrogenation; imines; quinolines
• ISSN: 1867-3880; 1867-3899
• DOI: 10.1002/cctc.201000078

This Review deals with the asymmetric hydrogenation and asymmetric transfer hydrogenation of imines and some nitrogen‐containing heteroaromatic compounds to afford amines. Hydrogenation and transfer hydrogenation are covered in separate sections. Particular attention is devoted to the substrates, since this reaction is highly substrate dependent. In this way the general structural trends in imine hydrogenation are presented, highlighting the more challenging substrates. Since hydrogenation of acyclic and cyclic (including heteroaromatic) imines have some different features they are also presented separately. The catalytic systems are classified according to the metal, and focus on the most successful catalytic systems and metal–ligand combinations. The catalytic cycles for these hydrogenation processes are also proposed. Imine business: An important method for the preparation of chiral imines, an important synthetic intermediate, is the asymmetric hydrogenation of CN double bonds using chiral transition metal complexes as catalysts. In recent years, interest in this reaction has grown considerably, resulting in more efficient processes and higher selectivities. In this Review, important recent advances are discussed.