Studies On Metal-free Photocatalyzed Dehydrogenative Cross-coupling Reaction :the Construction Of Quinoline Fused Lactone Derivatives

The cross-dehydrogenative coupling（CDC）reaction is one of the most straightforward and atom-economical strategies for forming C-C bonds through direct coupling of two C-H bonds.This type of reaction avoids the tedious prefunctionalization of the starting materials,and therefore largely reduces the number of reaction steps.Among these reactions,the direct oxidative C_sp3-_H functionalization of glycine derivatives has emerged as a viable method for the rapid synthesis ofα-substitutedα-amino acid derivatives and other useful compounds.Despite the progress made thus far,nevertheless,most of these protocols involve the use of stoichiometric amount of oxidants（i.e.,DDQ or t-BuOOH）,which leads to low atom economy and occurrence of toxic wastes;and some of them were performed at high temperature.Therefore,the development of sustainable and green catalytic versions for this type of reaction,is still highly desired.Centred on these key issues,we recently developed a new metal-free photocatalytic approach to the synthesis of quinoline fused lactones from glycine derivatives and 2,3-dihydrofuran..This thesis could be divided into the following two Parts:Chapter 1:The general methods for constructing C-C bond by CDC reaction were briefly reviewed.The CDC reactions were classified according to their reaction mechanism,which could be divided into Heck-type processes,direct arylations,ionic intermediates,radical intermediates or enzyme-Catalyzed Oxidative Coupling.This chapter mainly introduced the remarkable progress in this field.Finally,we also reviewed the photocatalytic CDC reactions.Chapter 2:A metal-free aerobic oxidative dehydrogenative coupling/annulation tandem reaction of glycine derivatives to 2,3-dihydrofuran was introdced.The process involves the synergistic performance of organic-dye-mediated photoredox catalysis and acid catalysis.After carefully screening of the reaction conditions,we finally chose the best conditions as:Eosin Y as the catalyst,10 M H₂SO₄ as the cocatalyst,CH₃CN as the solvent,under the irridation of 3W blue LEDs at room temperature and an air atmosphere.This reaction provides rapid and facile access to a series of valuable quinoline fused lactones in 40-86%yield at room temperature under air atmosphere.Moreover,the reaction could be performed on a 20 mmol scale,without obvious reduction of the yield.We also applied our method to the synthesis of quinoline fused lactam,which further demonstrated the practicability of our protocol.Given the inexpensive starting materials and catalyst,and the mild and operationally simple reaction conditions,this metal-free visible-light-induced protocol should find broad application in the synthesis of quinoline fused lactones.