Study On Palladium-Catalyzed Synthesis Of Fused Indoles From Aryl-Substituted Indoles

Fused indoles are an extremely significant class of nitrogen-containing heterocyclic compounds.Many optoelectronic materials and synthetic drug molecules contain the fused indole skeleton.Therefore,fused indole compounds have been widely concerned by scientific researchers for a long time,and they are also a research hotspot in the organic synthesis field.Traditional synthesis methods of fused indoles mostly rely on the cutting of carbon-halogen bonds on the indole skeleton.In recent years,direct C-H bond activation methodology has been development rapidly caused by the green chemistry synthesis concept.A large amount of alkylation,arylation and acylation about indole C2-C7 by direct C-H bond activation under transition metal catalysis have been reported.However,only a few research reports on the direct functionalization of indole C2-C7 and then domino cyclization to form fused indoles.Based on the above investigation results,this thesis carried out the use of palladium acetate as catalyst.A series of aryl indole(2-arylindole,1-methyl-2-arylindole,1-methyl-3-arylindole,N-arylindole,1-methyl-4-arylindole,7-arylindole)as starting materials to synthesize fused indoles.The research content of this paper includes the following three chapters:The first chapter,we summarized the application research progress and synthesis method research progress of fused indoles in recent years,as well as the selection basis and content of this topic.The second chapter,we developed a new method for the synthesis of indolo[1,2-f]phenanthridine from 2-arylindole and 2-bromobenzoic acid compounds by using palladium acetate as the catalyst,sodium carbonate as the base,DMA(N,N-dimethylacetamide)as the solvent,and reacting for 24 h under the oxygen atmosphere at 100 ~oC.By this method,indolo[1,2-f]phenanthridine,a kind of fused indoles,was successfully obtained through the construction of C-N bond and C-C bond.This reaction has the advantages of ligands free and oxygen being oxidant(clean and easily available).The third chapter is based on the synthesis of indole[1,2-f]phenanthridine,from the perspective of direct C-H bonds activation of indole C2 and C3,employ palladium acetate as the catalyst,2-bromobenzoic acid as the aryl source to synthesize fused indole skeleton by using N-aryl indole,1-methyl-2-aryl indole,1-methyl-3-aryl indole,1-methyl-4-aryl indole,7-aryl indole as the raw material.The synthesis of fused indoles substituted at different positions is realized,which have great significance for the analysis of the difficulty of indole activation at different positions.