Supramolecularly Regulated Ligands for Asymmetric Hydroformylations and Hydrogenations |
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| Authors: | Prof. Dr. Anton Vidal‐Ferran Dr. Ignasi Mon Antonio Bauzá Prof. Dr. Antonio Frontera Laura Rovira |
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| Affiliation: | 1. Institute of Chemical Research of Catalonia (ICIQ), Avgda. Pa?sos Catalans 16, 43007 Tarragona (Spain), Fax: (+34)?977920228;2. Catalan Institution for Research and Advanced Studies (ICREA), Passeig Lluís Companys 23, 08010 Barcelona (Spain);3. Departament de Química, Universitat de les Illes Balears (UIB), Cra. de Valldemossa, km 7.5. Palma, 07122 Palma de Mallorca (Spain) |
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| Abstract: | Herein we report the use of polyether binders as regulation agents (RAs) to enhance the enantioselectivity of rhodium‐catalyzed transformations. For reactions of diverse substrates mediated by rhodium complexes of the α,ω‐bisphosphite‐polyether ligands 1 – 5 , a – d , the enantiomeric excess (ee) of hydroformylations was increased by up to 82 % (substrate: vinyl benzoate, 96 % ee), and the ee value of hydrogenations was increased by up to 5 % (substrate: N‐(1‐(naphthalene‐1‐yl)vinyl)acetamide, 78 % ee). The ligand design enabled the regulation of enantioselectivity by generation of an array of catalysts that simultaneously preserve the advantages of a privileged structure in asymmetric catalysis and offer geometrically close catalytic sites. The highest enantioselectivities in the hydroformylation of vinyl acetate with ligand 4 b were achieved by using the Rb[B(3,5‐(CF3)2C6H3)4] (RbBArF) as the RA. The enantioselective hydrogenation of the substrates 10 required the rhodium catalysts derived from bisphosphites 3 a or 4 a , either alone or in combination with different RAs (sodium, cesium, or (R,R)‐bis(1‐phenylethyl)ammonium salts). This design approach was supported by results from computational studies. |
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| Keywords: | asymmetric catalysis enantioselectivity hydroformylation hydrogenation rhodium supramolecular chemistry |
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