Stitching phospholanes together piece by piece

• Verfasst von: Lloret Fillol, Julio [VerfasserIn]
• Verfasst von: Kruckenberg, Achim [VerfasserIn]
• Verfasst von: Scherl, Peter [VerfasserIn]
• Verfasst von: Wadepohl, Hubert [VerfasserIn]
• Verfasst von: Gade, Lutz H. [VerfasserIn]
• Titel: Stitching phospholanes together piece by piece
• Titelzusatz: new modular di- and tridentate stereodirecting ligands
• Verf.angabe: Dr. Julio Lloret Fillol, Achim Kruckenberg, Peter Scherl, Prof. Dr. Hubert Wadepohl and Prof. Dr. Lutz H. Gade
• E-Jahr: 2011
• Jahr: November 8, 2011
• Umfang: 16 S.
• Fussnoten: Gesehen am 02.11.2022
• Titel Quelle: Enthalten in: Chemistry - a European journal
• Ort Quelle: Weinheim : Wiley-VCH, 1995
• Jahr Quelle: 2011
• Band/Heft Quelle: 17(2011), 50 vom: Dez., Seite 14047-14062
• ISSN Quelle: 1521-3765
• DOI: doi:10.1002/chem.201101864
• Datenträger: Online-Ressource
• Sprache: eng
• Bibliogr. Hinweis: Erscheint auch als : Druck-Ausgabe: Stitching phospholanes together piece by piece. - 2011
• Sach-SW: asymmetric catalysis
• Sach-SW: hydrogenation
• Sach-SW: ligand design
• Sach-SW: phospholanes
• Sach-SW: rhodium
• K10plus-PPN: 1820479994

Abstract

The modular one-pot synthesis of a large family of bi- and tridentate 2,5-dimethyl- and 2,5-diphenyl-substituted phospholanes employs air-stable chiral phospholanium chloride salts and primary amines or NH4Cl as starting materials. These were transformed into the C2-symmetric dimethyl- and diphenylphospholane ligands, which reacted with [Rh(cod)2]BF4 (cod=1,5-cyclooctadiene) to yield the rhodium complexes [Rh(L)(cod)]BF4 (L=bisphospholane ligands). The corresponding trisphospholane complexes, 11 and 12, were obtained in high yields (81 and 92 %, respectively), and fully characterised by NMR spectroscopy, mass spectrometry and elemental analysis. Whilst in the C3-symmetric complex 11, containing the tridentate 2,5-dimethylphospholane, the ligand is bound symmetrically, different coordination behaviour was found for the diphenyl-substituted complex 12, in which the coordination of only two of the three phospholane moieties to the metal centre was observed. A DFT study at the B3PW91 level established minimum energy structures consistent with experimental findings in solution and in the solid state. The non-coordinated phospholane unit present in 12 allowed further modification of the complex through the coordination of AuIX (X=Cl, C6F5 and tris(trifluoromethyl)phenyl (FMes)) fragments to the pendant phosphane. To investigate the potential of the new ligands, the enantioselective hydrogenation of a series of prochiral olefins as benchmark substrates, using isolated Rh complexes as catalysts, was studied. The substrates included methyl esters of three dehydro-α-acetamido acids and two itaconic acid derivatives. In general good to excellent enantioselectivities (of up to >99 % ee) were observed. Ligand backbone modification by coordination of bulky AuX substituents to the free phospholane unit in complex 12 led to an outstanding enhancement of the catalyst performance and there was a clear correlation between the properties of the complex periphery and the enantioselectivity.