The Cross-Coupling Reaction Of Electron-Poor Terminal Alkynes And Oxidative Cleavage Of The Carbon-Carbon Triple Bond By Palladium-Catalyzed

The alkyne skeleton is a prevalent motif found in many naturally occurring products and materials. Among the methods for constructing this skeleton, the Sonogashira cross-coupling reaction represents as one of the most straightforward and efficient tools, and has been widely explored since it was reported by Sonogashira, Cassar and Heck independently. Although many modified transformations have been reported for these purposes, some limitations are still remained: electron-poor alkynes are usually provided unsatisfactory results from the reaction with aryl halides. Thus, the development of an efficient and ligand-free method for extending the electron-poor alkyne scope is interesting.The reactions of alkynes are a fundamental class of method for the formation of various carbon-carbon bonds and carbonheteroatom bonds in organic synthesis. Among the reactions of alkynes, however, routes to the cleavage of the carbon-carbon triple bond of alkynes have not been well-explored. Traditionally, the carbon-carbon triple bond is cleaved by ligating to metal complexes and oxidative cleavage using a stoichiometric amount of metal reagents, such as OsO4 or ozone. However, the metal complexes are expensive and poisonous, and ozone is not safe in the more scale. Thus, it is signified that development of a metal-catalyzed method for the oxidative cleavage of the carbon-carbon triple bond is desired.The contents of the dissertation include the following results.1 Palladium-catalyzed cross-coupling reaction of terminal alkynes with arylboronic acids has been described. In the presence of Pd(OAc)2 and Ag2O, a variety of terminal alkynes, including electron-poor terminal alkynes, smoothly underwent the reaction with numerous boronic acids to afford the corresponding internal alkynes in moderate to good yields. Moreover, this methodology was applied to the synthesis of 1H-isochromenes and diynes. It is noteworthy that the reaction proceeds under ligand-free and relative lower loading Pd conditions, and the maximal TONs (turnover numbers) of the reaction are up to 720,000.2 A new, general palladium-catalyzed oxidative cleavage of the carbon-carbon triple bond is presented. In the presence of PdCl2, CuCl2, TEMPO and air, a variety of 3-oxoprop-1-ynyl compounds lose an alkynyl carbon leading to 1,2-dicarbonyl compounds through an oxidative cleavage tandem process.