Study On The Construction Of C-S Bond And The Synthesis Of Nitrogen-containing Heterocyclic Compounds

The construction of the C-S bond is one of the important topics in organic synthetic chemistry and is the main approach to synthesize sulfur-containing compounds.Sulfur-containing compounds,including thioether,thiol,thiophenol,sulfonamide,sulfoxide,etc.,play an important role in the fields of biochemistry,medicinal chemistry,and polymer science.Therefore,how to construct the C-S bond using a simple and efficient method is one of the hot spots in the field of organic synthesis.Nitrogen-containing heterocyclic compounds are cyclic compounds containing at least one nitrogen atom in addition to carbon atoms in the molecule.The nitrogen-containing heterocyclic compounds are widely studied at present,and they are important structural skeletons of natural products,medicines and pesticides.Such compounds have unique biological activities,low toxicity,and high systemicity.They play an important role in the field of biological and pharmacological fields due to those unique biological activities.Therefore,exploring simple and convenient methods to synthesize nitrogen-containing heterocyclic compounds has become one of the research goals of many chemists.In this thesis,we focus on the construction of C-S bond on the 9 site of fluorene and the synthesis of quinolones,benzothiazoles,triazines and other nitrogenous heterocyclic compounds starting with simple and readily available reaction substrates.The first part is an introduction.We have summarized the current synthesis methods of C-S bonds and summarized the current research status of nitrogen-containing heterocyclic compounds.The second part introduces the study on the synthesis of 9-thiofluorene by iodine-catalyzed oxidized C-S bond cross-coupling.The highly efficient and selective C（sp³）–S bond cross-coupling method for the synthesis of 9-thiolated fluorenes through a direct thiolation at 9-C（sp³）–H of fluorenes under metal-free conditions with thiols is described.This reaction occurs at ambient conditions and shows good tolerance of functional groups including aryl thiols and alkylthiols.Besides,the reaction of benzothiophenol and fluorine generates unexpected9-benzylidene-9Hfluorene by eliminating hydrogen sulfide.This transformation features simple operation,mild reaction conditions,short reaction times,and environmental friendly.The third part introduces the study on the synthesis of 4-quinolone compounds by Rhodium-catalyzed[3+3]cycloaddition reaction.We report Rh（III）-catalyzed[3+3]annulation reactions for the preparation of functionalized 4-quinolones from N-nitrosoanilines and cyclopropenones via N-nitroso-directed C–H activation.A variety of 4-quinolone derivatives were prepared with good regioselectivity.The fourth part introduces the study on the synthesis of benzothiazole compounds by iodine-catalyzed three-component reaction.A novel and efficient iodine-catalyzed one-pot reaction of aromatic amines,acetophenones,and elemental sulfur for the synthesis of 2-aryl benzothiazoles is described.The process involves sequential C-S and C-N bond formation followed by C（CO）-C bond cleavage from readily accessible starting materials.In addition,2-aminonaphthalene was also suitable for this transformation,and the desired product2-phenylnaphtho[2,1-d]thiazole.This transformation features simple operation,mild reaction conditions,and cheap catalyst.The fifth part introduces the study on the synthesize 1,2,4-triazine compounds thought two different domino pathways.1,2,4-Triazine compounds were synthesized via two coupled domino strategies employing simple and readily available arylacetaldehydes/arylethyl alcohols as starting materials.In this reaction,2-phenylacetaldehyde is iodinated to 2-iodo-2-phenylacetaldehyde,which react with N-aminobenzidine to synthesize 1,2,4-triazine compounds.The reactions proceed smoothly in one pot with the advantages of high functional groups tolerance,available materials,and employing environmentally catalyst I₂.In addition,the protocols eliminate the need to prepare 1,2-dicarbonyl precursors.