Student Essay

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Reviews Reaction Mechanisms S. E. Denmark and G. L. Beutner DOI: 10.1002/anie.200604943 Lewis Base Catalysis in Organic Synthesis Scott E. Denmark* and Gregory L. Beutner Keywords: catalysis · donor–acceptor interactions · electrophilic · nucleophilic stereoselectivity Angewandte 1560 Chemie  2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Angew. Chem. Int. Ed. 2008, 47, 1560 – 1638 www.angewandte.org Lewis Base Catalysis Angewandte From the Contents 1. Introduction 2. Defining Lewis Base Catalysis 3. Lewis Acid–Base Interactions 4. Scope of the Review 5. Examples of Lewis Base Catalysis: The n–p* Interaction 1561 1563 1563 1568 Chemie The legacy of Gilbert Newton Lewis (1875–1946) pervades the lexicon of chemical bonding and reactivity. The power of his concept of donor–acceptor bonding is evident in the eponymous foundations of electron-pair acceptors (Lewis acids) and donors (Lewis bases). Lewis recognized that acids are not restricted to those substances that contain hydrogen (Brønsted acids), and helped overthrow the “modern cult of the proton”. His discovery ushered in the use of Lewis acids as reagents and catalysts for organic reactions. However, in recent years, the recognition that Lewis bases can also serve in this capacity has grown enormously. Most importantly, it has become increasingly apparent that the behavior of Lewis bases as agents for promoting chemical reactions is not merely as an electronic complement of the cognate Lewis acids: in fact Lewis bases are capable of enhancing both the electrophilic and nucleophilic character of molecules to which they are bound. This diversity of behavior leads to a remarkable versatility for the catalysis of reactions by Lewis bases. 1569 6. The n–s* Interaction: Lewis Base Catalysis with Polarized and Ionized Intermediates 1585 7. Lewis Base Catalysis Beyond

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