Diazonium Salts As Substrates In Palladium-Catalyzed C-C Coupling Reactions

Aromatic diazonium salts have been prepared and extensively usedfor years. They are both attractive and useful partners represent analternative to aryl halides or triflates because of their ready availabilityfrom anilines, superior reactivity and environmentally friendly.Arenediazonium salts are both attractive and useful partners inpalladium-catalyzed chemistry. So far, arenediazonium salts have beenused in a variety of palladium-catalyzed coupling reactions, includingMizoroki–Heck reactions, Suzuki–Miyaura and Stille crosscouplingreactions, etc.In chapter II，we display a new method concerning the study ofpalladium-catalyzed Hiyama cross-coupling reaction with arenediazonium salts to afford the corresponding biaryls in good yields under mildreaction conditions. The method is simple, efficient and very practicalwhich does not need the use of bases or ligands and the rigorousexclusion of air/moisture is not required. The transformation can tolerate different functional groups very well and either electron-donating orelectron-withdrawing group exhibited high reactivity. Theoretical studyof the reaction mechanism shows that the rate-limiting step of thecatalytic cycle is transmetalation in which tetrafluoroborate anion mayplay the role to attack the Si atom.In chapter III，there’s an efficient and a simple method to preparesymmetrical aryl biphenyls promoted by FeCl₂at60C with moderate togood yields. Different from the traditional protocols which always lead toside products, during our experiments single product was obtained byrunning the reaction directly in air without using additional oxygensource. Various biaryls were synthesized in good yields in short time inCCl4.