Supramolecularly Regulated Ligands for Asymmetric Hydroformylations and Hydrogenations

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 hydrof...

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Bibliographic Details
Published in:Chemistry : a European journal 2015-08, Vol.21 (32), p.11417-11426
Main Authors: Vidal-Ferran, Anton, Mon, Ignasi, Bauzá, Antonio, Frontera, Antonio, Rovira, Laura
Format: Article
Language:English
Subjects:
Acetic acid
Active sites
Ammonium
Ammonium salts
asymmetric catalysis
Asymmetry
Benzoates
Benzoic acid
Binders
Catalysis
Catalysts
Cesium
Chemical reactions
Chemistry
Computer applications
Enantiomers
enantioselectivity
hydroformylation
hydrogenation
Ligands
Naphthalene
Rhodium
Salts
Substrates
supramolecular chemistry
Vinyl acetate
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Summary: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. Polyether binders were used as regulation agents (RAs) to enhance the enantioselectivity of rhodium‐catalyzed hydroformylations and hydrogenations of an array of diversely substituted alkenes (see figure).
ISSN:0947-6539
1521-3765
DOI:10.1002/chem.201501441