Studies On Synthesis Of Diaryl Ethanones And Pyrano[2,3-c]pyrazolone Derivatives By Visible-light/N-Heterocyclic Carbenes Catalysis

N-Heterocyclic carbenes(NHCs)catalysts can be used for the conversion of various unsaturated compounds,including aldehydes,imines,acyl chlorides and activated esters.The electron pair transfer catalytic reactions involved in the catalysis of N-hetero-cyclic carbenes have been extensively studied.However,NHCs-catalyzed reactions through the single electron transfer(SET)process are challenging.In this paper,the following research work has been done on the synergistic catalysis of visible light and NHCs:Chapter 1.The literature research on the catalytic modes of visible-light/NHCs synergistic catalysis is carried out,and the research progress of synergistic catalytic reactions in recent years is summarized.Chapter 2.The free radical reaction of(1H-benzo[d][1,2,3]triazol-1-yl)(phenyl)-methanone derivatives and substituted phenylacetic acid catalyzed by photoredox/NHCs are developed.A series of diaryl ethanones were synthesized by coupling reaction with high yield(up to 92%).The reaction has the characteristics of mild conditions,wide substrate applicability,and large-scale synthesis,which provides a new method for the synthesis of aryl substituted ketones.Preliminary research on the reaction mechanism was carried out through controlled experiments,and a reasonable reaction mechanism was proposed.Chapter 3.We developed the [4+2] cycloaddition reaction of α-diazone and pyrazolonederived oxadiene compounds through sequential visible-light/NHC with good yields(up to94%),high diastereoselectivity(>20:1 dr).A series of functionalized pyrano[2,3-c]-pyrazolone derivatives were synthesized.In addition,the asymmetrical catalytic synthesis of pyran[2,3-c]pyrazolone was explored,and which was obtained with high diastereoselectivity(>20:1)and moderate enantioselectivity(up to 55% ee).The further optimization of reaction conditions are still in progress.The research results expand the application of visible-light/NHCs relay catalysis in organic synthesis.