Decarboxylative Functionalizations Of Benzoic Acids Via Using Transition-metal Copper As Catalyst

Since carboxylic acids have distinguishing features of low cost, non-toxicity and ready availability. In recent decades, transition-metal-catalyzed decarboxylative coupling reactions of carboxylic acids have been rapidly developed. Compared with the traditional coupling reagents, organometallic intermediates generated from the decarboxylative transformations served as either nucleophiles or electrophiles, depending on the nature of employed transition-metal catalyst in decarboxylative reactions. In addition, the decarboxylative coupling reactions extrusion of CO2 as a nontoxic waste product, which is satisfied with the requirement of green chemistry. Therefore, transition metal-catalyzed decarboxylative coupling has become an important method for the formation of C–C and C–X(X = heteroatom) bonds.Generally, Pd、Ag、Rh、Au and other precious metal are commonly used as catalysts for the decarboxylative coupling reactions, which lead to the high cost of the decarboxylative coupling reactions. Therefore, it is necessary to develop cheap metal catalyzed decarboxylation couping of carboxylic acids, Considering that copper is cheap transition-metal, we decide to develop a series of decarboxylative functionalizations of benzoic acids via using copper as catalyst.The research work in this thesis mainly includes the following parts: 1) simple protocol for Cu-catalyzed protodecarboxylation of(hetero)aromatic carboxylic acids under mild conditions;2) facile synthesis of 2,2`-dinitrosubstituted biaryls through Cu-catalyzed ligand-free decarboxylative homocoupling of ortho-nitrobenzoic acids; 3) Pd-catalyzed decarboxylative methylthiolation of aromatic carboxylic acids by using DMSO as the sulfurizing reagent; 4) decarboxylative halogenation and cyanation of electron-deficient aryl carboxylic acids via Cu mediator as well as electron-rich ones through Pd catalyst under aerobic conditions.