title: Supramolecularly Regulated Ligands for Asymmetric Hydroformylations and Hydrogenations.
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)2 C6 H3)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.
authors.affiliation: Institute of Chemical Research of Catalonia (ICIQ), Avgda. Països Catalans 16, 43007 Tarragona (Spain), Fax: (+34) 977920228. avidal@iciq.cat.|Catalan Institution for Research and Advanced Studies (ICREA), Passeig Lluís Companys 23, 08010 Barcelona (Spain). avidal@iciq.cat.
authors.forename: Anton
authors.initials: A
authors.lastname: Vidal-Ferran
authors.affiliation: Institute of Chemical Research of Catalonia (ICIQ), Avgda. Països Catalans 16, 43007 Tarragona (Spain), Fax: (+34) 977920228.
authors.forename: Ignasi
authors.initials: I
authors.lastname: Mon
authors.affiliation: Departament de Química, Universitat de les Illes Balears (UIB), Cra. de Valldemossa, km 7.5. Palma, 07122 Palma de Mallorca (Spain).
authors.forename: Antonio
authors.initials: A
authors.lastname: Bauzá
authors.affiliation: Departament de Química, Universitat de les Illes Balears (UIB), Cra. de Valldemossa, km 7.5. Palma, 07122 Palma de Mallorca (Spain).
authors.forename: Antonio
authors.initials: A
authors.lastname: Frontera
authors.affiliation: Institute of Chemical Research of Catalonia (ICIQ), Avgda. Països Catalans 16, 43007 Tarragona (Spain), Fax: (+34) 977920228.
authors.forename: Laura
authors.initials: L
authors.lastname: Rovira
keywords: asymmetric catalysis; enantioselectivity; hydroformylation; hydrogenation; rhodium; supramolecular chemistry