Construction Of Nitrogen Heterocyclic Compounds By Photo-promoted Radical Cyclization Reaction

Nitrogen heterocyclic compounds are an important class of organic compounds and important active ingredients in drug molecules.Among them,quinoline and phenanthridine azacyclic compounds have very wide applications in organic synthesis and drug molecular structure,and have been one of the hot spots of research in the past decades.However,the traditional synthetic methods still have some shortcomings,such as harsh reaction conditions,high energy consumption and high environmental costs.Therefore,there is still a need to explore new and green research methods for the synthesis of such azacyclic compounds.In this work,using glycine esters and dimethyl sulfoxide as radical precursors to construct quinoline and phenazopyridine compounds by radical addition cyclization reaction under light conditions were proposed.And the reaction was well generalized and extended to obtain 21 quinoline-based derivatives.1.The developments in construction of quinoline esters by photopromoted radical cyclization reactionIn the past decade,photocatalyzed ortho nitrogen of amine compounds Significant progress has been made in the functionalization of theα-C（sp³）-H bond.On this basis,in this study,arylglycine esters were used as substrates,24W blue light as light source,rose red as photosensitizer,and o-nitrogenα-C（sp³）-H bond of arylglycine esters was activated to form free radical precursors.Quinoline derivatives were obtained by free-radical addition cyclization with alkyne esters,with the highest yield of 93%.The structures of the target compounds were determined by ¹H NMR,¹³C NMR and LC-MS.The reaction can be carried out at room temperature and under air atmosphere,while avoiding the use of metal catalysts,providing a clean and green pathway for the synthesis of quinoline-like compounds.2.The developments in construction of 6-methylphenanthridines by photopromoted radical cyclization reactionThe reaction conditions were discussed in this part.Biphenyl isonitrile was used as the reaction substrate,24W blue light as the light source,ruthenium（Ⅱ）as the photosensitizer,triethylamine as the additive,Dimethyl sulfoxide as both the reaction solvent and the methyl radical source.The reaction was carried out in oxygen atmosphere for 24 hours,and 6-methylphenanthroline compounds were obtained through free-radical addition cyclization.This reaction has good universality and has been extended to obtain18 6-methylphenanthroline derivatives,with a maximum yield of 89%;The structure of the target compound was determined by ¹H NMR,¹³C NMR,and X-ray single crystal diffraction（XRD）.The mild reaction conditions provide a simple,economical,and effective approach for the synthesis of 6-methylphenanthridine and its derivatives.Figure[58]Table[11]Reference[123]...