Construction Of Carbon-and Sulfur-Stereocenters Via Palladium-catalyzed C-H Activation

It is very challenging to realize highly stereoselective hydrocarbon bond functionalization because of the high bonding energy of carbon hydrogen bonds and the similar chemical environment of carbon hydrogen bonds in molecules.The transition metal-catalyzed asymmetric carbon-hydrogen bond activation based on the guiding strategy has become a scientific research front,mono-and bidentate directing groups are important in different enantioselective C-H activation protocol.In this article,we paid attention on Pd（Ⅱ）-catalyzed asymmetric C-H functionalizations enabled by directing group to construct chiral carbon and sulfur centers.Two parts are as below:（1）Palladium-catalyzed asymmetric arylation of inert methylene C-H bondsIn this study,we synthesized chiralβ-arylcarboxylic acid derivatives by palladium asymmetric C-H bond arylation using PIP as bidentate directing group and chiral 3,3’-F₂-Binol as ligand in a mixed solvent of tert-butanol and toluene.The reaction has the advantages of cheap raw materials,wide range of substrates,high enantioselectivity and cheap ligands.We hope that this method can provide a new idea for the discovery of other types of stereoselective C-H functionalization reactions.（2）Palladium catalyzed asymmetric C-H alkenylation to construct chiral sulfoxideIn this study,we achieved the kinetic resolution of chiral sulfoxide enabled by palladium catalyzed asymmetric C-H alkenylation.We use pyridine as the monodentate directing group,L-p Glu-OH as the chiral ligand and acrylate as the alkenylation reagent.This reaction has a wide range of substrates,mild reaction conditions and good tolerance of functional groups.The synthesized chiral sulfoxide skeleton are common in medical and catalyst.