Iridium-Catalyzed Asymmetric Hydrogenation
In this chapter, we describe the development in homogeneous Ir-catalyzed asymmetric hydrogenation with particular emphasis on the achievements made during the last 10 years. We also present their application to the synthesis of complex molecules. The firs
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Iridium-Catalyzed Asymmetric Hydrogenation Jèssica Margalef, Oscar Pàmies, and Montserrat Diéguez
Contents 1 Introduction 2 Ir-Catalyzed Asymmetric Hydrogenation of Unfunctionalized Olefins or with Poorly Coordinative Groups 2.1 Di- and Trisubstituted Unfunctionalized Olefins or with Poorly Coordinative Groups 2.2 Tetrasubstituted Unfunctionalized Olefins or with Poorly Coordinative Groups 3 Ir-Catalyzed Asymmetric Hydrogenation of Olefins Containing Coordinating Groups 3.1 Ir-Catalyzed Asymmetric Hydrogenation of Carboxylic Acids 3.2 Ir-Catalyzed Asymmetric Hydrogenation of Nitroolefins 3.3 Ir-Catalyzed Asymmetric Hydrogenation of Enamines, Enamides, and Allylic Amines 4 Asymmetric Ir-Catalyzed Hydrogenation of Imines 4.1 Asymmetric Hydrogenation Using Cationic Catalyst Precursors 4.2 Asymmetric Hydrogenation Using Neutral Catalyst Precursors 5 Ir-Catalyzed Asymmetric Hydrogenation of Ketones 5.1 P-Donor-Based Ligands 5.2 Non-P-Donor-Based Ligands 6 Conclusions References
Abstract In this chapter, we describe the development in homogeneous Ir-catalyzed asymmetric hydrogenation with particular emphasis on the achievements made during the last 10 years. We also present their application to the synthesis of complex molecules. The first section deals with the hydrogenation of unfunctionalized olefins or with poorly coordinative groups. The second section includes the advances made in the hydrogenation of functionalized olefins. The last two sections cover the hydrogenation of imines and ketones, respectively.
J. Margalef, O. Pàmies, and M. Diéguez (*) Departament de Química Física i Inorgànica, Universitat Rovira i Virgili, Tarragona, Spain e-mail: [email protected]
J. Margalef et al.
Keywords (Un)functionalized olefins · Asymmetric hydrogenation · Catalysis · Imines · Iridium · Ketones
1 Introduction Metal-catalyzed asymmetric hydrogenation (AH) offers some of the most sustainable and straightforward reactions for producing pharmaceuticals, flavors, fragrances, agrochemicals, and fine chemicals due to its perfect atom economy and operational simplicity [1–5]. It is estimated that around 10% of all chemical steps in the synthesis of these compounds are hydrogenations. Despite the extensive research dedicated to the asymmetric hydrogenation and the important progress reached, some issues still need to be solved. Most catalysts only work with a limited number of substrates, and each type of substrates needs a specific catalyst for optimal enantioselectivity. For example, the asymmetric hydrogenation of functionalized alkenes is mostly carried out by Ru- and Rh-diphosphine catalysts (see, e.g., [6–9]), while the asymmetric hydrogenation of unfunctionalized olefins or with poorly coordinative groups is mainly carried out with Ir-P,N catalysts (for reviews, see [10–15]). A broad substrate scope is desirable to reduce the time dedicated to ligand/ catalyst design and preparation. A desired additional condition is that the catalyst family should be synthesized from available starting materials and be easy to handle. The n
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