Mechanistic Studies On Electrochemical Functionalization Of Cycloamines And Carboxylation With Carbon Dioxide

Redox reactions are one of the most important types of reactions in the field of chemistry and are widely used in the synthesis of various natural products and complex molecules.Compared to traditional methods,electrochemical redox reactions use green and clean electrical energy to replace toxic oxidizing and reducing reagents,require simple equipments and mild reaction conditions,have good atom economy and environmental friendliness,these features make them more advantageous in industrial production.During my master’s studies,I achieved the oxidative functionalization of cyclic amines,dehalogenative carboxylation of halobenzenes,and ring-opening carboxylation of epoxides using electrochemical synthesis methods,then conducted detailed mechanistic studies and proposed possible reaction pathways.Specifically,this master’s thesis is divided into the following parts:The development of organic electrochemistry and related mechanistic research methods,as well as recent research progress on amine functionalization methods and CO₂-involved organic carboxylation reactions are briefly introduced in Chapter one.An electrochemical-driven method forβ-functionalization of cyclic amines,which is simple,mild,and has good functional group compatibility is presented in Chapter two.By using cyclic voltammetry,linear sweep voltammetry,and other mechanistic investigation methods,I identified the transformation pathway of the reaction substrate in the system and revealed the key catalytic role of ferrocene,proposing a possible reaction mechanism:cyclic amines are directly oxidized on the anode to generate enamines,while benzoylformic acid forms a complex with ferrocene,which then decarboxylates to generate a radical.The radical couples with the enamine to produce the final functionalized cyclic amine product.A strategy for the electroreductive carboxylation of aromatic carbon-halogen bonds,catalyzed by a catalytic amount of naphthalene as an organic mediator is presented in Chapter three.Through this electrolysis method,various bromobenzenes and chlorobenzenes containing different electron-donating or withdrawing groups could be successfully dehalogenated and carboxylated to the corresponding carboxylic acid molecules,achieving a significant breakthrough in the efficient synthesis of carboxylic acids.Through controlled experiments and electrochemical analysis,I confirmed that naphthalene acted as an electron transfer mediator in the system,proposing a rational reaction mechanism:naphthalene molecules are directly reduced on the cathode to generate naphthalene free radical anions and further reduce aryl halides to generate carbon anions.The carbon anions are attacked by CO₂ and undergo an acidification step to generate the final carboxylic acid products.An electrochemical-driven method for the ring-opening carboxylation of aryl epoxides is described in Chapter four,which achieves the efficient and highly selective synthesis of important chemical products:β-hydroxy carboxylic acids.The reaction has mild conditions and good substrate compatibility.Through controlled experiments,cyclic voltammetry and other electrochemical analysis methods,I analyzed the effects of different parameters on the reaction results and proposed different reaction processes based on the different reduction potentials of the various epoxides:epoxides with lower reduction potentials are directly reduced on the cathode to carbon anions and then combined with CO₂ to generate carboxylate salts.For epoxides with higher reduction potentials,their reduction process is driven by CO₂ radical anions.The main content and innovation of the full text is summarized in Chapter five,further proving the significance of the topics.This thesis included 68 figures,16 tables,and 148 references.