Visible-light Induced Direct Benzylic C(sp~3)-h Activation For Synthesis Of Benzo[α]carbazoles From Tetrahydronaphthalene

The benzo[a]carbazoles have considerable attention from both organic synthetic and medicinal chemists due to their diverse biological and unique optical properties.In recent years,several synthesis approaches have been reported,however,most of these previous methods suffer from some limitations:lengthy synthesis sequences,metal-catalyzed,harsh reaction conditions and poor functional group tolerance et al.Consequently,it is still highly desirable to explore new synthetic protocols accomplished under environmentally friendly and mild reaction conditions to access the benzo[a]carbazoles.This thesis mainly describes the photocatalytic synthesis of benzo[a]carbazoles via visible-light induced direct benzylic sp³C-H activation and cycloaddition/oxidative aromatization sequence from 1,2,3,4-tetrahydronaphthalene and arylhydrazine hydrochlorides.It consists of three chapters.In the first chapter,the general routes for the synthesis of benzo[a]carbazoles were introduced with an emphasis on the recent progress in the related research field,and were summarized according to the synthetic differences of various rings of benzo[a]carbazole compounds.In view of the existing synthetic methodologies situations,we proposed the direction of our research.In the second chapter,the specific content of the thesis research was described.We put forward the synthesis of benzo[a]carbazoles via visible-light induced direct benzylic C（sp3）-H activation from1,2,3,4-tetrahydronaphthalene,comprehensively discussed the factors affecting the experimental results,explored the possible reaction mechanism and the adaptability of methodologies.To optimization the reaction conditions,tetrahydronaphthalene and arylhydrazine hydrochlorides were as model substrates.Based on the examination of the experimental parameters,the optimized reaction conditions for the model reaction was that 10-phenyl-9-（2,4,6-trimethylphenyl）acridinium tetrafluoroborate as photocatalyst,O₂ as the oxidant,acetonitrile/water as a mixed solvent,room temperature,blue LEDs light.On this basis,a total of 31 benzo[a]carbazole compounds with different substituents were obtained.The experimental procedure was simple and the highest yield was 78%.Thus,a approach for the synthesis of benzo[a]carbazoles using O₂ as the oxidant was developed under mild conditions without metal catalyst,which had a wide range of substrate applications,could be performed on gram scale and used to synthesize biologically active molecules.The third chapter provided the experimental part,including the equipment,consumables and the detailed synthesis of catalyst,tetrahydronaphthalene and substituted phenylhydrazine used in the research process.And the related compounds were charactered by ¹H NMR,¹³C NMR and HRMS,compound 3da was consistent with the speculated structure by the simultaneous X-ray single crystal.