Preparation of novel axially chiral NHC–Pd(II) complexes and their application in oxidative kinetic resolution of secondary alcohols

Abstract

Novel axially chiral N-heterocyclic carbene (NHC) Pd(II) complexes were prepared from optically active 1,1 -binaphthalenyl-2,2 -diamine (BINAM) and H 8 -BINAM and their crystal structures were unambiguously determined by X-ray diffraction. These chiral N-heterocyclic carbene (NHC) Pd(II) complexes were applied in the oxidative kinetic resolution of secondary alcohols using molecular oxygen as a terminal oxidant or under aerobic conditions, affording the corresponding sec-alcohols in good yields with moderate to good enantioselectivities.

Chemical Exchange Saturation Transfer (CEST) as a Tool to Measure Ligand Flexibility of Chelating Chiral Di-N-heterocyclic Carbene Complexes

“…Chiral di- N -heterocyclic carbene (diNHC) ligands bind a metal via two M–carbene bonds with the carbene heterocycles tethered typically by a chiral fragment. A recent surge in application of chiral diNHC–metal complexes in asymmetric catalysis − prompted studies to develop a method to quantify the relative flexibility within the linking unit of diNHC ligands.…”

Synthesis of Chiral Bis(N-heterocyclic carbene) Palladium and Rhodium Complexes with 1,1′-Biphenyl Scaffold and Their Application in Asymmetric Catalysis

“…in asymmetric catalysis, the design of chiral C 2 -symmetric bidentate ligands has been an important strategy for the development of chiral ligands, which can significantly reduce the number of possible isomeric metal complexes, different substrate−catalyst arrangements, and reaction pathways. Compared to the rapid development of monodentate NHC ligands combined with coordination groups , such as oxazoline and phosphine, the development of chiral C 2 -symmetric bis(NHC) ligands has not received much attation. , …”

Recent Developments in the Applications of Palladium Complexes Bearing N-Heterocyclic Carbene Ligands

“…88,89 Given the importance of indole derivatives in biology, [90][91][92] The same group has also studied the oxidative kinetic resolution of sec-alcohols using chiral Pd(II)-NHC complexes and molecular oxygen as a oxidant. [93][94][95] As an example, the axially chiral Pd(II)-NHC complex 29 was tested in the oxidative kinetic resolution of a wide range of sec-alcohols affording the corresponding alcohols in moderate conversions (48-68%) and moderate to high ee's (53-94%). …”