The Studies On Construction And Rearrangement Reactions Of N,O-Diaryl Active Intermediates

NOBIN-type Biaryls are widely found in biologically active natural products,pharmaceutical molecules,and organic functional materials.In particular,axially chiral biaryls are widely used as organic ligands and catalysts.Therefore,it is of great significance to synthesize various biaryl compounds,and related research have also attracted widespread attention of chemists.Traditional synthetic methods mainly rely on transition metal-catalyzed cross-coupling reactions and carbon-hydrogen bond arylation reactions.Most of them require metal catalysts,which are high-cost,and the removal of metal residues poses great challenges in drug development.It does not meet the concept of green chemistry.To this end,our goal is to find an economical,simple,and green approach to construct biaryl compounds.After continuous attempts,we have developed a tandem strategy to NOBIN-type biaryl compounds through a N,O-diaryl active intermediate that rapidly undergos a[3,3]-sigmatropic rearrangement.This strategy realizes two different kinds of electrophiles as reaction substrates,which react with arylhydroxylamines or aryloxylamines,respectively,to achieve the efficient synthesis of a series of NOBIN analogues.The research contents are mainly divided into the following two parts:In the first part,the C-N bond has a high bond energy,it is still difficult to use transition metal-catalyzed method to break the C-N bond.The more effective method is to convert the amine compounds into ammonium salts.Quaternary ammonium salts with the advantages of stability,safe operation and easy preparation,makes the cross-coupling reaction with various nucleophiles through C-N bond cleavage become a hot research topic in recent years.We use potassium tert-butoxide as base,dimethyl sulfoxide as solvent under mild conditions in the absence of metal catalysts at 25? to achieve an highly efficient[3,3]-sigmatropic rearrangement reaction of electrophilic reagents-aryl quaternary ammonium salts with easily prepared aryl hydroxylamine.Moreover,this reaction has the advantages of mild conditions,rapid reaction,good functional group compatibility and high yieldsIn the second part,diaryliodonium salts have many unique advantages,such as mildness,low toxicity,stable properties,easy preparation,and environmental friendliness.In addition,it is a highly active electrophilic arylation reagent.Therefore,we use diaryliodonium salts as the substrate reacting with the nucleophilic aryloxyamine to form a highly active N O-diaryl intermediate that undergos a[3,3]-rearrangement to form a series of highly functionalized compounds with NOBIN frameworks.This strategy uses cesium carbonate as the base and 1,2-dichloroalkane as the solvent,two kinds of biaryl compounds can be synthesized with or without metal catalysts at 30?.The substrate scope is very wide and the resulting products have great potential for further conversion to brand-new atropoisomeric biaryl compounds and heterocycles.