Study On Elemental Sulfur Promoted The Cascade Reaction Of Diamination And Dehydroaromatization Of Cyclohexanone

As special aromatic amine structures,N,N'-disubstituted o-arylenediamines have emerged as core frameworks of a series of bioactive molecules and synthetic precursors of functional materials and ligands.It is because of their far-reaching application,that more and more attention has been paid to their efficient synthesis.However,the most common method is still the transition-metal catalyzed C-N cross coupling between nucleophilic amines and halogenated compounds.Although these classical reactions have many issues,such as limited substrates range,high cost of precious metals and residual transition-metals in products,they are still hard to be replaced in practical applications because of their better availability and repeatability.Being cheap and easily available bulk chemical raw materials,cyclohexanones have been widely used as potential aromatic sources to synthesize various high value-added aromatic compounds in recent years,and the relevant reports provide a feasible access to various aromatic amines.However,these reactions often require precious metals and highly functional substrates,and mostly afford monoamines.Based on the research foundation of our group in the aromatization of cyclohexanone,this paper focuses on the research work of cyclohexanone double amination,focusing on the selective amination and dehydroaromatization of cyclohexanone without the participation of transition metal catalyst.,this paper mainly includes the following two parts:1.Develop an elemental sulfur-promoted diamination and dehydroaromatization cascade reaction of cyclohexanones under aerobic conditions,which realize an efficient conversion of cheap and easily obtained cyclohexanones and arylamines into high value-added N,N'-diaryl-o-arylenediamines.This reaction avoid the use of metal and shows good substrate scope and functional group tolerance.It can also be conducted in a gram-scale with a good yield.2.Developed an elemental sulfur-promoted aerobic dehydrogenative access to N,N'-dialkyl-o-phenylenediamines from readily available cyclohexanones and aliphatic amines.This reaction avoids the the additions of transition metal and excessive base.Importantly,alkylamines are tolerated in this reaction,which show low reactivity in our previous system.The reaction conditions are also suitable for the synthesis of Nsubstituted 2-naphthylamine by monoamination of 2-tetralon and amines.