Sustainable Radical Cascade Reactions To Synthesize Multi-functionalized Pyrrole [1,2-a] Indoles

Pyrrole[1,2-a]indoles are important key structural components that are widely founded in the pharmaceutical,pesticide,and dye industry.Meanwhile,the skeleton compounds is a basic structural unit of many natural drugs active molecules and drug molecule intermediates,such as unique antitumor activity of mitomycin family compounds,the active natural products Yuremaine,the antimicrobial compound Isoborreverine.In this respect,great effort has been devoted to the development of efficient methods toward these unique skeletons but the development of-more efficient,simple synthesis method is still a lot of chemists' goal.Herein,we reported sustainable efficient access to synthesize difluoroalkylated pyrrolo[1,2-a]indoles and sulfonyl pyrrolo[1,2-a]indoles under mild conditions.(1)Sustainable difluoroalkylation cyclization cascades of 1,8-enynes:we reported a visible-light-induced difluoroalkylation and cyclization cascade reaction of 1,8-enynes with broad substrate scopes.This method provides a sustainable and efficient access to the synthesis of difluoroalkylated pyrrolo[1,2-a]indoles under mild conditions.Gram-scale experiment was conducted which yield the desired product in a reasonable isolated yield of 80%.(2)Sustainable radical cascades to synthesize difluoroalkylated pyrrolo[1,2-a]indoles:we disclosed herein a photocatalytic difluoroalkylation and cyclization cascade reaction of indolyl acrylates with broad substrate scopes.This method provides an efficient access to synthesize difluoroalkylated pyrrolo[1,2-a]indoles with a quaternary carbon center under mild conditions.(3)Alkyl radical triggered in situ SO2-capture cascades:we documented herein an in situ SO2-capture cascades triggered by alkyl radicals,using 1,8-alkyne as a substrate,FeC12 as a catalyst,and DTBP as oxidant.A wide range of alkylsulfonyl substituted pyrrolo[l,2-a]indoles were easily prepared with high yields and good functional group tolerability.Functional groups,such as CF3,CN,CO2Me or OCF3,were well tolerated.(4)Sustainable hydroperfluoroalkylation of unactivated alkenes triggered by radical fragmentation of enol triflates:we disclosed herein a photocatalytic hydroperfluoroalkylation of unactivated alkenes with internal triflyl group as CF3 radical source.This method provides a sustainable and efficient access to series of distantly perfluoroalkylated chromone derivatives through a radical/1,6-hydride transfer reaction under mild conditions.This method utilizes readily available starting materials,is easy to handle,and features a wide substrate scope.