Pd-Catalyzed Decarboxylative Ortho-C-H Functionalization Of 2-Nitro-benzoic Acids By Using Carboxylic Acid As The Traceless Directing Group

Transition-metal catalyzed C-H bond activation reaction can be used to construct structural frameworks including C-C,C-X,C-N and C-O bonds,etc.Thus,C-H bond functionalization plays an important role in organic synthesis.Recently,a variety of reports for transition-metal catalyzed C-H bond activation were developed,involving the use of carboxyl groups as the directing group,because of the stability and economical efficiency of carboxylic acid,and coordination of the carboxyl group with transition metal.In addition,such transition-metal catalyzed C-H activation with carboxyl as directing group generate products,which can play important role in biological,medical and other fields.Transition-metal catalyzed C-H activation with carboxyl as directing group,which refers to the coordination of oxygen of carboxyl with metal atom,and the carboxyl can be ultimately retained or removed under different conditions.Thus,it is a good synthetic strategy that ortho-C-H functionalization of benzoic acid with carboxyl as directing group initially,followed by decarboxylative protoantion in the presence of metal catalyst.In this paper,we have developed C-H functionalization of 2-nitro-benzoic acids,and carboxyl was employed as a traceless directing group to achieve C6 C-H bond functionalization of the substrate in the presence of Pd catalyst.It has been demonstrated that two Pd/Cu promoted synthetic methods with using carboxyl as traceless directing group in our paper,firstly,C6-halogenation and decarboxylative protonation of 2-nitrobenzoic acids;secondly,C6-methylthiolation and decarboxylative protonation of 2-nitrobenzoic acids with DMSO.