Feng chiralN,N′-dioxide ligands: uniqueness and impacts

Abstract

In historical perspective, all widely accepted privileged chiral ligands tune the catalytic activity of the metal complexes and impart stereoselectivity to asymmetric reactions exclusively relying on the coordination with phosphorus...

Asymmetric catalytic Friedel–Crafts alkylation with arenes and heteroarenes: construction of 3,3-disubstituted oxindoles

“…Based on the previous reports, 15–17 a plausible catalytic cycle and a stereo-control model have been proposed (Fig. 2).…”

Design and Synthesis of Rigid‐Featured Tertiary Amine‐Derived C2‐Symmetric Chiral Furan‐N,N′‐dioxide Ligands

“…It is widely recognized that deployment of symmetry [6] and scaffold rigidity [7] are frequently used principles in the design of privileged chiral ligands, because chiral ligands with symmetry and rigid backbones can generally minimize the potential number of isomers produced of any ligand-metal-substrate complex by minimizing the number of potential reaction pathways, thus imparting excellent levels of stereocontrol. [6,8] Adhering to such approaches has proven to be successful and as aided in the discovery of several privileged ligands, including bis (oxazolines), bis(phosphine) compounds, and spirobiindane based ligands. [6][7][8] Recently, we developed the first rigid-featured tertiary amine-derived C 2 -symmetric chiral tridentate pyridine-N,N'dioxide (Py-2NO) ligands (Scheme 1c) [9a] and applied it in enantioselective the asymmetric Friedel-Crafts alkylation reactions.…”

“…[6,8] Adhering to such approaches has proven to be successful and as aided in the discovery of several privileged ligands, including bis (oxazolines), bis(phosphine) compounds, and spirobiindane based ligands. [6][7][8] Recently, we developed the first rigid-featured tertiary amine-derived C 2 -symmetric chiral tridentate pyridine-N,N'dioxide (Py-2NO) ligands (Scheme 1c) [9a] and applied it in enantioselective the asymmetric Friedel-Crafts alkylation reactions. Such a catalyst system tolerates air and moisture, and the reaction can be carried out without special handling such as glove box operation or moisture/oxygen free conditions.…”

Design of rigid chiral bipyridine-2NO tetradentate ligands: application in asymmetric catalysis

“…2,2′-Bipyridine N -oxides as catalytic ligands meet the difficulty of versatility, 8,9 whereas tertiary amine oxides might suffer from the installation of a new stereocenter at nitrogen. 10 A significant breakthrough was made by Feng's group, 11 who established a library of tertiary amine-derived flexible 2NO ligands, where inclusion of the amide N –H bond can anchor the chirality at nitrogen stereocenters through intramolecular hydrogen bonding. They act as neutral tetradentate ligands to bind a wide variety of metal ions and enable an intriguing and easily fine-tuned chiral platform for a variety of asymmetric catalytic reactions (Scheme 1b).…”