Enantioselective Synthesis Of Atropisomers Featuring Pentatomic Heteroaromatics By Asymmetric C-H Functionalization

In recent years,the development of chiral biaryl structures has attracted wide attention,and the application of these structures in chiral catalysts and ligands has also made important progress,especially in the field of catalytic asymmetry based on the axially chiral framework of phosphorus ligands.However,the traditional methods to construct chiral biaryl backbones were mainly limited to the construction of six-membered biaryl structure.In sharp contrast,the construction of atropisomeric species featuring one or even two five-membered rings is more challgening.This situation is basically due to the increased distance between the ortho-substituents next to the axis,which is responsible for lower barriers to rotation,hampering the conformational stability.Transition metal catalyzed directed asymmetric C-H activation in organic chemistry has become the most effective strategy for the synthesis of various natural products and important structures for its high atomic utilization.In this paper,the construction of atropisomeric species featuring one or even two five-membered rings is guided by the asymmetric C-H functionalization based on directing strategies.1.Enantioselective Synthesis of Atropisomers Featuring Pentatomic Heteroaromatics by Pd-Catalyzed Asymmetric C-H AlkynylationWe have developed a Pd(?)-catalyzed asymmetric C-H alkynylation for the construction of atropisomeric species featuring one or even two five-membered rings using aldehyde as the directing group and the L-tert-leucine as a catalytic transient chiral auxiliary.The reaction condition is mild and was found to be compatible with a wide range of substrates.It is efficient to construct a series of compouds featuring one or even two five-membered rings connected variously through a C-C or C-N,such as N-arylpyrroles and 3,3'-bisbenzothiophene.This reaction provides an efficient,direct and highly economical method for the construction of atropisomers featuring pentatomic heteroaromatics by means of asymmetric C-H functionalization.2.Enantioselective Synthesis of Atropisomers Featuring Pentatomic Heteroaromatics by Pd-Catalyzed Asymmetric C-H AllylationIn this study,the L-tert-leucine were used as a catalytic transient chiral auxiliary,and asymmetric allylation catalyzed by Pd(?)was developed to successfully construct the biaryl chiral compounds containing five-membered heterocycles.