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Relevant academic research and scientific papers

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 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. One ligand - two chiral binding sites: A library of new, chiral, bridged cyclophosphazane ligands, in which chirality can be introduced at two positions (at the bridge and/or at the phosphorus bridging amido groups), gives rise to good enantiomeric ratios in AuI- and Ni0-catalyzed enentioselective reactions (see scheme, Ts=tosyl). Copyright

The more gold-the more enantioselective: Cyclohydroaminations of γ-allenyl sulfonamides with mono-, bis-, and trisphospholane gold(I) catalysts

A series of chiral mono-, di-, and trinuclear gold(I) complexes have been prepared and used as precatalysts in the asymmetric cyclohydroamination of N-protected γ-allenyl sulfonamides. The stereodirecting ligands were mono-, di-, and tridentate 2,5-diphen

Gold(I)-catalyzed enantioselective intramolecular hydroamination of allenes

The asymmetric intramolecular hydroamination of allenes catalyzed by phosphinegold(I)-bis-p-nitrobenzoate complexes is described. This reaction is applicable to the enantioselective formation of vinyl pyrrolidines and piperidines in 70-99% ee. Copyright