Diverse Synthesis Of Biaryl Axis Chiral Compounds Via Transition-Metal Catalysis

As one kind of important axially chiral compounds,biaryl atropisomers are widely existing in natural products and active biomolecules,and are also the core skeleton of myriad of famous ligands or catalysts.A classification into nonbridged and bridged biaryls is obvious for structural reasons.At present,the methods for constructing biaryl axially chiral mainly include de novo synthesis of aromatic rings,asymmetric aryl-aryl cross-coupling reactions,oxidative dimerization reactions,desymmetrization,and(dynamic)kinetic resolution.The researches in this thesis mainly based on transition metal catalysis to construct biaryl axially chiral compounds.It is divided into two parts:the first one,study on palladium-catalyzed enantioselective synthesis of 2-aryl cyclohex-2-enone atropisomers"platform molecule";the second,study on Cu-catalyzed Sommelet-Hauser rearrangement.Chapter 1:Besides oxidative dimerization reactions,asymmetric aryl-aryl cross-coupling reactions are among the most accessible and straightforward methods for the construction of biaryl atropisomers.One of the biggest challenges in this area is the limited range of possible substrates.For example,if the nature of the ortho substituents was changed,and the new catalyst systems were required to achieve satisfied enantioselectivity.In order to overcome the limitations of the classical coupling reaction generality,our group proposed a strategy for synthesizing"platform molecules":synthesizing other kinds of axially chiral molecules through the same molecular diversity.Based on the atropisomers of the styrene-arene skeleton,we have completed the synthesis of biaryl axially chiral compounds based on the atropisomers of a,P-unsaturated keto-arene skeleton.Highly enantioselective synthesis of the less rigid 2-arylcyclohexenone axially chiral"platform molecules" using the modified BoPhoz ligand was realized.The"platform molecule"was derivatized to synthesize biaryl axially chiral compounds with different ortho substituents such as phenols,carbazoles,aniline carbonates,benzoquinones and iodobenzenes with high ee values.Chapter 2:The achiral biaryl six-membered cyclic compound and the chiral metal carbene generate nitrogen ylide in situ,then the reaction produced a spiro product through Sommelet-Hauser rearrangement that competes with Stevens rearrangement.The existing literature has only reported one case of constructing a spiro compound by Sommelet-Hauser rearrangement,and there are many problems such as poor selectivity and generality of the reaction.We reported a biaryl torsional strain promotes copper-catalyzed Sommelet-Hauser rearrangement and the selectivity and generality of the reaction were dramatically improved.The products can be further derivatized into alcohols,polycyclic compounds and so on.Studies of model reactions have shown that torsional strain greatly promotes Sommelet-Hauser rearrangement,which enhances the understanding of the reaction mechanism.