Study On Copper Catalyzed C-S Coupling Reaction And Synthesis Of Sulfur Heterocyclic Compounds

The formation of C-S bonds is playing a key role in the synthesis of compounds with sulfur, so the C-S cross-coupling reactions have a significance in methodology.Transition metals, especially Pd and Ni, catalyzed C-S cross-coupling reactions have been widely investigated in the past three decades. As copper is low-cost and easy to obtain compared to Pd and Ni, copper-catalyzed C-S cross-coupling reactions are always hot topic. Because the lower active of copper catalyst, copper-catalyzed cross-coupling reactions have been limited in the coupling of aryl iodides and activated aryl bromides with thiols. The keystone and difficulty are to employ cheaper and more widely available aryl bromides and chlorides as arylating agents and control the selectivity of coupling.Our research goal is to find an efficient copper-catalyzed system for C-S cross-coupling of aromatic thiols with inactivated aryl bromides and chlorides and control the selectivity of coupling.Through optimizing the reaction conditions, we got the effective reaction conditions for C-S cross-coupling with copper catalyst and ligand: ArBr or ArCl (0.75 mmol), ArSH (0.5 mmol), CuBr (20 mol%), Ligand 1,2,3,4-tetrahydroquinoline-8-o1 (20 mol%), Cs2CO3 (1.0 mmol), DMF (1.5 mL),130℃,48 h under argon. With the optimized conditions, a variety of thioethers as well as symmetrical and unsymmetrical bis-thioethers were obtained in excellent yields by using cheaper aryl bromides and chlorides. Experimental results indicate that this system has an exceptional functional group tolerance and high chemoselectivity.Encouraged by the success of above research subject, we synthesize the [1]benzothieno[3,2-b][1]benzothiophene (BTBT) and benzothiophene (BT) compounds with o-bromoarylyne and sodium sulfide through closed-loop reaction of addition and coupling.