Construction Of C–C Bonds Via Decarboxylative Reactions Of Organic Acids With Alkynes

In the field of organic synthesis, transition-metal-catalyzed cross-coupling reactions have been recognized as an important strategy for constructing new carbon-carbon and carbon-heteroatom bonds. Compared with the traditional cross-coupling reactions, the decarboxylative coupling reactions have some unique advantages: organic acids derivatives are easily available and stable to be handled and stored. In addition, the byproducts in the decarboxylative coupling reactions are carbon dioxide. During the past dacades, the common transition metals, such as Pd, Cu, Ru, Rh and the others, can be used to efficiently catalyze the decarboxylative coupling reactions of organic acids, which have been applied to the synthesis of natural products, bioactive compounds and materials as well. Very recenltly, a more green synthetic strategy,visible-light-initiated organic synthetic reactions, have been established for generating new organic molecules. However, only few examples of visible-light induced decarboxylative reactions that are reported to date. Therefore, this thesis mainly focuses on the decarboxylative reactions of organic acids with alkynes, the following contents were included:(1) A Ru-catalyzed decarboxylative cyclozation of α-keto acids with alkenes in the presence of Piv OH and Cu(OAc)2 was well established for constructing isocoumarins,which showed high functional group tolerance and good to excellent yields. It is important to note that the dual roles of COOH serving as both directing group and leaving group were observed in the reactions.(2) An efficient and mild silver-promoted decarboxylative coupling reactions of inactive aliphatic carboxylic acids with bromoacetylenes at room temperature was developed, which showed high functional group tolerance and provided an alternative route to the asymmetric internal alkynes in good to excellent yields.(3) A novel and practical hypervalent iodine(III) reagent catalyzed decarboxylative formation of carbon-carbon bond with α-keto acids and bromoacetylenes by sunlight irradiation at room temperature has been established. Mechanistic study demonstratesthat the sunlight-driven decarboxylation undergoes a radical process with the generation of ynones in good yields.