Iridium-Catalyzed Allylic Alkylation Reaction with N-Aryl Phosphoramidite Ligands: Scope and Mechanistic Studies

Abstract

A series of N-aryl phosphoramidite ligands has been synthesized and applied to iridium-catalyzed allylic alkylation reactions, offering high regio- and enantioselectivities for a wide variety of substrates. These ligands feature the synthetic convenience and good tolerance of the ortho-substituted cinnamyl carbonates. Mechanistic studies, including DFT calculations and X-ray crystallographic analyses of the (π-allyl)-Ir complexes, reveal that the active iridacycle is formed via C(sp(2))-H bond activation.

Asymmetric trapping of zwitterionic intermediates by sulphur ylides in a palladium-catalysed decarboxylation-cycloaddition sequence

“…5b) might be subjected to interference by the additional electrolyte. The combination of Pd and BINOL-derived chiral phosphoramidites has been developed into a privileged catalyst in asymmetric organic transformations 39 over the past 20 years. Significantly, many reactive Pd-allyl phosphoramidite complexes have been isolated, and their configurations have been established through X-ray diffraction (see Supplementary Fig.…”

Catalytic Asymmetric Dearomatization by Transition-Metal Catalysis: A Method for Transformations of Aromatic Compounds

“…Inspired by the elegant work by Bandini et al 19 on the enantioselective synthesis of tetrahydrocarbolines via Pd-catalyzed intramolecular allylic substitution, we envisioned that, in the presence of an appropriate chiral Ir catalyst, tryptamine-derived allylic carbonates 4 might undergo intramolecular allylic dearomatization reactions, delivering six-membered-ring spiroindolenines 5. 20 After systematic evaluations of the reaction conditions, it was revealed that utilizing [Ir(cod)Cl] 2 (cod = cyclooctadiene) as the iridium precursor in combination with a chiral phosphoramidite ligand Me-THQphos (R,R a )-L2 developed by our group 21,22 could afford the desired dearomatized products smoothly in high yields and with excellent diastereo-and enantioselectivity (up to >99:1 diastereomeric ratio and 96% ee) (Scheme 2). Later, we further identified that the substrate scope of this reaction could be largely broadened by application of an Ru-based catalyst.…”

Enantio-, Diastereo-, and Regioselective Iridium-Catalyzed Asymmetric Allylic Alkylation of Acyclic β-Ketoesters

“…Recently, our group demonstrated the power of iridium- N -arylphosphoramidite catalysis 8 in accessing vicinal all-carbon quaternary and tertiary stereocenters with our report on the regio-, diastereo- and enantioselective asymmetric allylic alkylation of cyclic β-ketoesters (Scheme 1a). 7b, 9, 10 The success of this protocol combined with the virtual absence of reports describing the application of this transformation to acyclic β-ketoesters encouraged our further exploration of iridium catalysts in the domain of this important substrate class.…”