Chiral ditopic cyclophosphazane (CycloP) ligands: synthesis, coordination chemistry, and application in asymmetric catalysis
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...
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| Main Authors: | , , , |
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
August 28, 2013
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| In: |
Chemistry - a European journal
Year: 2013, Volume: 19, Issue: 41, Pages: 13823-13837 |
| ISSN: | 1521-3765 |
| DOI: | 10.1002/chem.201302327 |
| Online Access: | Verlag, lizenzpflichtig, Volltext: https://doi.org/10.1002/chem.201302327 Verlag, lizenzpflichtig, Volltext: https://onlinelibrary.wiley.com/doi/abs/10.1002/chem.201302327 
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| Author Notes: | Torsten Roth, Hubert Wadepohl, Dominic S. Wright, and Lutz H. Gade |
| Summary: | 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. |
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| Item Description: | Gesehen am 20.01.2022 |
| Physical Description: | Online Resource |
| ISSN: | 1521-3765 |
| DOI: | 10.1002/chem.201302327 |