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In chemistry, transfer hydrogenation is a chemical reaction involving the addition of hydrogen to a compound from a source other than molecular H2. It is applied in laboratory and industrial organic synthesis to saturate organic compounds and reduce ketones to alcohols, and imines to amines. It avoids the need for high-pressure molecular H2 used in conventional hydrogenation. Transfer hydrogenation usually occurs at mild temperature and pressure conditions using organic or organometallic catalysts, many of which are chiral, allowing efficient asymmetric synthesis. It uses hydrogen donor compounds such as formic acid, isopropanol or dihydroanthracene, dehydrogenating them to CO2, acetone, or anthracene respectively. Often, the donor molecules also function as solvents for the reaction. A large scale application of transfer hydrogenation is coal liquefaction using "donor solvents" such as tetralin.
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Asymmetric hydrogenation is a chemical reaction that adds two atoms of hydrogen to a target (substrate) molecule with three-dimensional spatial selectivity. Critically, this selectivity does not come from the target molecule itself, but from other reagents or catalysts present in the reaction. This allows spatial information to transfer from one molecule to the target, forming the product as a single enantiomer. The chiral information is most commonly contained in a catalyst and, in this case, the information in a single molecule of catalyst may be transferred to many substrate molecules, amplifying the amount of chiral information present. Similar processes occur in nature, where a chiral molecule like an enzyme can catalyse the introduction of a chiral centre to give a product as a single enantiomer, such as amino acids, that a cell needs to function. By imitating this process, chemists can generate many novel synthetic molecules that interact with biological systems in specific ways, leading to new pharmaceutical agents and agrochemicals. The importance of asymmetric hydrogenation in both academia and industry contributed to two of its pioneers — William Standish Knowles and Ryōji Noyori — being awarded one half of the 2001 Nobel Prize in Chemistry.
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Benjamin List is a German chemist who is one of the directors of the Max Planck Institute for Coal Research and professor of organic chemistry at the University of Cologne. He co-developed organocatalysis, a method of accelerating chemical reactions and making them more efficient. He shared the 2021 Nobel Prize in Chemistry with David MacMillan "for the development of asymmetric organocatalysis".
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References
- ↑ Pfaltz, Andreas (1999). "From Corrin Chemistry to Asymmetric Catalysis - A Personal Account". Synlett. 1999 (S1): 835–842. doi:10.1055/s-1999-3122.
- ↑ Helmchen, Günter (5 May 2008). "Andreas Pfaltz: on the Occasion of his 60th Birthday". Advanced Synthesis & Catalysis. 350 (7–8): 951–952. doi: 10.1002/adsc.200800113 .
- ↑ Rasetti, Vittorio; Hilpert, Kurt; Fässler, Alexander; Pfaltz, Andreas; Eschenmoser, Albert (1 December 1981). "The Dihydrocorphinol→ Corrin Ring Contraction: A Potentially Biomimetic Mode of Formation of the Corrin Structure". Angewandte Chemie International Edition in English. 20 (12): 1058–1060. doi:10.1002/anie.198110581.
- ↑ Pfaltz, Andreas; Jaun, Bernhard; Fassler, Alexander; Eschenmoser, Albert; Jaenchen, Rolf; Gilles, Hans Harald; Diekert, Gabriele; Thauer, Rudolf K. (5 May 1982). "Zur Kenntnis des Faktors F430 aus methanogenen Bakterien: Struktur des porphinoiden Ligandsystems". Helvetica Chimica Acta. 65 (3): 828–865. doi:10.1002/hlca.19820650320.
- ↑ Fritschi, Hugo; Leutenegger, Urs; Pfaltz, Andreas (1 November 1986). "Chiral Copper-Semicorrin Complexes as Enantioselective Catalysts for the Cyclopropanation of Olefins by Diazo Compounds". Angewandte Chemie International Edition in English. 25 (11): 1005–1006. doi:10.1002/anie.198610051.
- ↑ Pfaltz, Andreas (1 June 1993). "Chiral semicorrins and related nitrogen heterocycles as ligands in asymmetric catalysis". Accounts of Chemical Research. 26 (6): 339–345. doi:10.1021/ar00030a007.
- ↑ Helmchen, Günter; Pfaltz, Andreas (2000). "PhosphinooxazolinesA New Class of Versatile, Modular P,N-Ligands for Asymmetric Catalysis". Accounts of Chemical Research. 33 (6): 336–345. doi:10.1021/ar9900865. PMID 10891051.
- ↑ von Matt, Peter; Pfaltz, Andreas (1 April 1993). "Chiral Phosphinoaryldihydrooxazoles as Ligands in Asymmetric Catalysis: Pd-Catalyzed Allylic Substitution". Angewandte Chemie International Edition in English. 32 (4): 566–568. doi:10.1002/anie.199305661.
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