Carbon Dioxide Involved In The Synthesis Of Fluorinated Carboxylic Acids And Chiral Cyclic Carbonates

Carbon dioxide is the major greenhouse gas.It is also a cheap and renewable carbon source.The chemical fixation of carbon dioxide into value-added fine chemicals is one of the most significant routes to develop the green carbon science and carbon neutrality.This dissertation focuses on the synthesis of fluorinated carboxylic acids and chiral cyclic carbonates with carbon dioxide as a C1 synthon.The detailed research works are introduced as following:1)An effective Cu-catalyzed stereoselective defluorinative carboxylation reaction of gem-difluoroalkenes with carbon dioxide was reported in the presence of10 mol%Xantphos/Cu I as catalyst,aryl and alkenyl substituted gem-difluoroalkenes were compatible,diverse important?-fluoroacrylic acids were obtained in 57-97%yields with perfect Z-selectivity.The reaction might go through a borylation and carboxylation process.In addition,control experiments shown that a trans-?-F elimination should be involved for monofluoroalkenes.2)However,the use of stoichiometric bases and reductants compromised the efficiency of copper catalytic system.We reported a facile synthesis of?-fluoroacrylic esters via direct electrochemical defluorinative carboxylation of gem-difluoroalkenes with carbon dioxide,using a platinum plate as working cathode and a cheap nickel plate as anode in a user-friendly undivided cell,affording the desired adducts in up to83%yield and>20:1 Z/E ratio.A cyclic voltammetry study was conducted and suggested a novel process(single-electron reduction,reaction with carbon dioxide,single-electron reduction,loss of fluoride).3)The carboxylation of C-H bonds is one of the most direct ways to synthesize the acids,using carbon dioxide as a carboxylative reagent.On the basis of electroauxiliary,a highly regioselective C-H bonds carboxylation of monofluoroalkenyl substituted arenes with carbon dioxide was preliminarily studied.The reaction was performed with cheap Ni-sheet as working cathode and graphite felt as anode,containing ⁿBu₄NI as the supporting electrolyte.Control experiments shown that the iodine anion in the electrolyte was vital to this transformation.It was further proposed that the reaction may undergo a process of in suit generated active iodine species.Additionally,the electrochemical carboxylation of C-H bonds in benzothiazole was also preliminarily studied.4)A novel catalytic asymmetric carboxylative cyclization of 1-indanone derived racemic propargylic alcohols with carbon dioxide was realized,based on a kinetic resolution strategy,both optically active tertiary propargylic alcohols and chiral cyclic carbonates could be obtained simultaneously with considerable yield and moderate enantioselectivity in the presence of Ag OAc and chiral Schiff base ligands.