Studies Of Iron (Ⅲ)-catalyzed Synthesis Of Benzoxazines And Axial Chiral Quinoxalines From 2-arylindoles

Indole is one of the most important nitrogen heterocyclic compounds in heterocyclic compounds.Indole skeletons exist in many drug molecules and natural products.Some studies have found that indole derivatives have very significant anti-inflammatory,anti-hormonal and anti-viral effects,and can be widely used in drug production,perfumes,dyes and medical industries.In addition,indole compounds are easily available,and as intermediates and building blocks,they play a very important role in organic synthesis.The research on indole skeleton transformation has also attracted the interest of many synthetic organic chemists.We mainly focus on the construction of N-heterocyclic compounds with 2-arylindoles,the synthesis of axial chiral quinoxalines and their application as ligands in the synthesis of N-alkenylaldonitrones.Our content is divided into three parts:In the first part,a strategy to synthesize indole-fused benzoxazine compounds from 2-aryl indoles and o-aminophenols through iron(III)catalyzed C3-H amination and intramolecular cyclization was developed.We discussed the effects of temperature,catalyst,solvent and other conditions on the reaction.At the same time,the substrate scope of the reaction was studied and It was found that the reaction has the advantages of short reaction time,good functional group compatibility,and easy operation.This strategy provides a more efficient and convenient method for the synthesis of indole-fused benzoxazine compounds.In the second part,we developed a C3-H nirtosation reaction mediated by tert-butyl nitrite(TBN)and subsequent iron(III)catalyzed C-N bond cleavage to prepare various types of axial chiral quinoxaline compounds from 2-arylindoles and orthobenzenediamines under the mild reaction condition.This strategy features gram scale preparation,good functional group compatibility,broad substrate scope and easily available starting materials.This strategy provides a simple and effective method for the construction of axis chiral quinoxaline compounds.In the third part,a series of axis chiral quinoxaline imine ligands were designed and synthesized,and they were used to catalyze the coupling reaction of N-alkenyl boronic acids and cinnamaldehyde oximes to synthesize N-alkenyl aldonitrones.We discussed the efficiency of different quinoxaline ligands on synthesis of N-alkenyl nitrones by the electronic effects and steric effects.Experiments showed that the quinoxalineimine ligands with axial chirality are more effective in the coupling reaction.It has the advantages of wide range of functional group tolerance,simple operation,broad substrate scopes,which solves the synthetical problem of N-alkenyl cinnamaldehyde nitrones.This strategy provides a more efficient and practical method for the synthesis of N-alkenylnitrone compounds.