Inexpensive Metal Catalyzed Cross-Dehydrogenation Coupling And Cross-Decarboxylation Coupling Reactions To Synthesize Biheteroaryl Compounds

Biaryl compounds are widely found in polymer materials,dyestuff,pharmaceuticals and natural products.It obtains heterocyclic compounds by replacing the carbon atom on the aromatic ring with N,O,and S atoms.The introduction of the hetero atom increases the electron cloud density of the aromatic ring,so that the C-H bond on the aromatic ring could activate without directing group.It could provide a theoretical basis for the construction of biaryl compounds by CDC reaction.In recent years,transition metal catalyzed C-H bond functionalization has been a hot spot,and most of them were catalyzed by noble metal catalysts such as Pd,Pt,Rh,Ru,Ir,etc.Cobalt catalysts are widely used for its low cost,low toxicity and unique reaction mechanism,which makes it a great advantage in the reaction of catalyzing the activation of C-H bonds to construct C-C bonds.Transition metal-catalyzed cross-dehydrogenation coupling and cross-decarboxylation coupling reactions are the most ideal green chemical reactions.The by-products of such reactions are H2O and CO2 ideally,which are consistent with the sustainable thought of chemical development.Therefore,the study of cross-dehydrogenation coupling and cross-decarboxylation coupling has become one of the most trending topics in organic chemistry.The first chapter of the paper mainly summarizes the physical and chemical properties and the application value of biaryl heterocyclic compounds,and introduces development processes for the synthesis of heteroaryls by transition metal catalysis.The cross-dehydrogenation coupling(CDC)reaction produces very little waste and by-products and does not require pre-functionalization of the reaction substrates,providing higher atomic and economic effects.In the second chapter,we mainly studied the bimetallic catalytic system of Ni or Co and Cu,with oxygen in the air as oxidant and assisted by sodium acetate,we synthesized biheteroarene compound benzoxazole-benzothiazole by cross-dehydrogenation coupling method.Transition metal catalyzed decarboxylation cross-coupling has become a versatile method in organic synthetic chemistry.In the third chapter,the cross-decarboxylation coupling reaction of electron-rich aryl carboxylic acid with heteroaromatic ring compound catalyzed by CoBr2 system is introduced.The key to this reaction is the use of N-heterocyclic carbene ligand,which inhibits the homo-coupling after Ag-promoted decarboxylation and assists in the process by which Co catalyzes the activation of C-H bond,increasing the yield of the reaction.