Visible-light-Catalyzed C3-H Functionalization Of Quinoxaline-2(1H)-One Scaffold

Visible-light-catalyzed photoredox reactions feature simple operation,mild conditions and environmental protection.Its application potential in the functionalization of heterocyclic compounds has become increasingly prominent.Quinoxaline-2(1H)-one C3 derivatives have important biological activity and chemical application value in the fields of medicinal chemistry,natural product chemistry and biochemistry.Therefore,it is of great significance to develop a visible-light-catalyzed method for the direct functionalization of the C3-H of the quinoxalin-2(1H)-one backbone.This thesis reviews the research progress of visiblelight-catalyzed quinoxaline-2(1H)-one skeleton C3-H bond functionalization reactions,and successfully developed a new strategy for the synthesis of C3-methylated and C3-difluorolactamylated quinoxalin-2(1H)-one derivatives by visible light catalysis,the main work includes the following two aspects:1)The direct C3-H methylation of quinoxaline-2(1H)-one skeleton has been achieved for the first time using N,N,N’,N’-tetramethylenediamine(TMEDA)as a new methyl source under visible light catalysis.This strategy has the characteristics of mild reaction conditions,simple operation and strong scalability.The mechanism study revealed that the reaction underwent continuous photoredox,alkali-assisted proton transfer,cleavage and tautomerization.2)Based on the visible light catalysis strategy,the visible light induced radical cascade cyclization of N-allyl bromodifluoroacetamide and quinoxalin-2(1H)-one was designed,and a new class of quinoxalin-2(1H)-one/3,3-difluoro-γ-lactam was constructed under mild conditions.It expands the chemical space of complex heterocycles with potential biological activity and provides new chemical entities for subsequent drug discovery.