Asymmetric catalysis. Part 128: Diastereomeric rhodium(I) complexes in the enantioselective hydrogenation of ketopantolactone |
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| Institution: | 1. Department of Chemistry and Biomolecular Sciences, Macquarie University, Sydney 2109, Australia;2. Mark Wainwright Analytical Centre, University of New South Wales, Sydney 2052, Australia;1. School of Chemistry and Chemical Engineering, Anhui University of Technology, Maanshan 243002, China;2. International Cooperation Base of Pesticide and Green Synthesis (Hubei), Key Laboratory of Pesticide & Chemical Biology (CCNU), Ministry of Education, Department of Chemistry, Central China Normal University, Wuhan 430079, China;3. Ocean College, Beibu Gulf University, Qinzhou 535011, China;4. Key Laboratory of Theoretical Chemistry and Molecular Simulation of Ministry of Education, Hunan University of Science and Technology, Xiangtan 411201, China;1. Key Laboratory of Polymer Matrix Composites, Heilongjiang Province, College of Materials Science and Engineering, Qiqihar University, Wenhua Street 42, Qiqihar, Heilongjiang, 161006, China;2. Niigata University, Faculty of Engineering, Ikarashi 2-8050, Nishi-ku, Niigata, 950-2181, Japan;3. College of Communications and Electronics Engineering, Qiqihar University, Wenhua Street 42, Qiqihar, Heilongjiang, 161006, China |
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| Abstract: | In the hydrogenation of ketopantolactone, new rhodium complexes bearing (R,R)-diop and various bidentate chiral N,N′ co-ligands with (R)- or (S)-configuration were used. On the one hand, the N,N′ co-ligands consist of pyrroleimines, which derive from (R)- and (S)-1-phenylethylamine, (R)- and (S)-1-cyclohexylethylamine (and benzylamine), and on the other hand of pyrroleoxazolines and pyridineimines. Stereoselectivities of 31–33% ee for (R)-pantolactone were achieved using related compounds (RR-R) and (RR-S), respectively, with no double stereoselectivity being observed. It is assumed that during catalysis the pyrroleimines bind in a monodentate way at the sixth coordination site of the rhodium atom by the pyrrole nitrogen with the imine nitrogen carrying the different chiral substituents far away from the rhodium atom. Monodentate deltacyclane phosphanes, chloro ligands or solvent molecules, bound at the sixth coordination site of the catalyst, led to widely differing enantioselectivities in the ketopantolactone hydrogenation. |
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