Organocatalytic N-Arylation Of Phenothiazines And Phenoxazines

Phenothiazines are a class of nitrogen and sulfur-based heterocyclic compounds.Due to the butterfly-shaped structure,large (?)-conjugated electroactive rigid framework and high molar absorption coefficient,they have been widely used in the dye industry,biomedicine and optoelectronics.In addition,N-phenyl phenothiazine and its derivatives show significant reduction ability,which can be used as a substitute for expensive iridium photocatalysts,and can be used in free radical dehalogenation of unactivated aryl halides.There are four main strategies for the synthesis of N-arylphenothiazines: 1.Transition-metal-catalyzed N-arylation of phenothiazines and aryl halides;2.Construction of N-arylphenothiazines by cyclization reaction;3.Organocatalytic dehydrogenation cross-coupling of phenothiazines and phenols;4.Electrochemically oxidized dehydrogenation cross-coupling of phenothiazines and phenols.However,most of these strategies require metal catalysts,oxidants or high reaction temperatures,and the scope of substrates is limited.In response to the above problems,this thesis is based on the azoarenes developed by our research group,reacting phenothiazines or phenoxazines with azoaromatics to construct N-arylphenothiazines and N-arylphenoxazines.This method which using chloroform as the solvent and diphenyl phosphate as the catalyst realized the high efficient N-arylation of phenothiazines and phenoxazines under mild conditions,the reaction yield is up to 98%.This strategy avoids the use of oxidants and expensive metal catalysts,has higher atom economy,less pollution to the environment,and has the advantages of fast reaction rate and wide substrate range.In the subsequent amplification effect and catalyst cycle experiment,it shows good yield and cycle activity,and has the potential for industrialization.In this project,a wide range of N-arylphenothiazines and N-arylphenoxazines were successfully synthesized by organocatalytic N-arylation reaction.The initial investigation on the asymmetric N-arylation of phenothiazines and phenoxazines was researched,and the configurational stability of the chiral product was also studied.