Synthesis Of Organic Sulfur/Selenium Compounds Based On Imidazo Heterocycles Skeleton

Imidazoheterocycles are often recognized as ubiquitous structural motif presenting in numerous natural products,medicine and functional materials.They are widely occured in numerous biological molecules possessing excellent bioactivities,such as antimicrobial,antiviral,antiparasitic,and antitumor properties.Therefore,much attention has been paid to developing the modification of imidazo heterocycles in recent years for the better biological activity.In this paper,a series of sulfenylimidazo[1,2-a] pyridines were synthesized by using elemental sulfur / selenium,which is environmentally friendly and efficient.Most importantly,the antitumor activities of some compounds were evaluated by conventional MTT assays.(1)Copper-catalyzed one-pot synthesis of chalcogen-benzothiazoles/ imidazo[1,2-a]pyridines with sulfur/selenium powder and aryl boronic acidsAn efficient and convenient route to access 2-chalcogen-benzothiazoles and 3-chalcogen-imidazo[1,2-a]-pyridines via copper-catalyzed oxidative chalcogenation of imidazo[1,2a]pyridines/benzothiazoles with sulfur/selenium powder and aryl boronic acids was reported.We sysnthesised 32 kinds of new imidazoheterocycles and all of them have been characterized by NMR,HRMS,IR and melting point.And the possible mechanism of the reaction was deliberated through a series of control experiments.In addition,some synthesized compounds displayed antitumor activity by a MTT assay.(2)Oxidative dual C–H selenation of imidazoheterocycles via a radical pathwayA novel DCP-mediated oxidative radical dual C–H selenation using selenium powder has been developed.The reaction was realized by the free radical coupling reaction of imidazoheterocycles with ethers/alkanes and Se powder under mild reaction conditions.It provides a wide range of structurally diversed imidazo heterocycles in good yields and with good functional group tolerance.And,all of the compounds in this reaction were characterized by NMR,HRMS,IR,and melting points.In addition,it has been conducted a series of control experiments for the reaction mechanism.(3)Catalyst free oxidative dual C-H sulfenylation of imidazoheterocyclesWe reported a catalyst and additive-free method for three-component crosscoupling reaction using imidazo[1,2-a]-pyridine,the arylamines(or arenols)and elemental sulfur to obtain unsymmetrical sulfides under the mild reaction conditions up to 42 examples were synthesized under the optimal conditions.And it exhibits excellent functional group tolerance and wide range of substrate extensions.Moreover,all of the obtained structures in this reaction have been determined by NMR,HRMS,IR,and melting point methods.Finally,in order to gain insight of the reaction mechanism of dual C-S bond formation,several control experiments have been conducted under different condition.