Chiral ditopic cyclophosphazane (CycloP) ligands

• Verfasst von: Roth, Torsten [VerfasserIn]
• Verfasst von: Wadepohl, Hubert [VerfasserIn]
• Verfasst von: Wright, Dominic S. [VerfasserIn]
• Verfasst von: Gade, Lutz H. [VerfasserIn]
• Titel: Chiral ditopic cyclophosphazane (CycloP) ligands
• Titelzusatz: synthesis, coordination chemistry, and application in asymmetric catalysis
• Verf.angabe: Torsten Roth, Hubert Wadepohl, Dominic S. Wright, and Lutz H. Gade
• E-Jahr: 2013
• Jahr: August 28, 2013
• Umfang: 15 S.
• Fussnoten: Gesehen am 20.01.2022
• Titel Quelle: Enthalten in: Chemistry - a European journal
• Ort Quelle: Weinheim : Wiley-VCH, 1995
• Jahr Quelle: 2013
• Band/Heft Quelle: 19(2013), 41 vom: 4. Okt., Seite 13823-13837
• ISSN Quelle: 1521-3765
• DOI: doi:10.1002/chem.201302327
• Datenträger: Online-Ressource
• Sprache: eng
• Sach-SW: asymmetric catalysis
• Sach-SW: chiral ligands
• Sach-SW: phosphazanes
• Sach-SW: synthetic methods
• Sach-SW: X-ray diffraction
• K10plus-PPN: 1786585065

Abstract

A series of dichlorocyclophosphazanes [ClP(μ-NR)2] containing chiral and achiral R groups was obtained from simple commercially available amines and PCl3. Their condensation reactions with axially chiral biaryl diols yielded ansa-bridged chiral cyclophosphazane (CycloP) ligands. This highly modular methodology allows extensive elaboration of the ligand set, in which the chirality can be introduced at the diol bridge and/or the amido R group. This provides the possibility to observe match and mismatch effects in catalysis. A series of twenty CycloP ligands was synthesized and characterized by multinuclear NMR spectroscopy, HRMS, elemental analysis, and in selected cases, single-crystal X-ray diffraction. These studies show that all of the ditopic CycloP ligands are C2 symmetric, rendering their metal coordination sites symmetry equivalent. Two well-established enantioselective reactions were explored by using late-transition metal CycloP complexes as catalysts; the gold-catalyzed hydroamination of γ-allenyl sulfonamides and the asymmetric nickel-catalyzed three-component coupling of a diene and an aldehyde. The steric demands of the CycloP ligands have a subtle influence on the reactivity and selectivity observed in both reactions. Good enantiomeric ratios (e.r.) as high as 89:11 in the gold-catalyzed reaction and 92:8 in the nickel-catalyzed bis-homoallylation reaction were observed.