Browsing by Subject "C-H activation"
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Item Palladium-catalyzed carbon-hydrogen bond functionalization utilizing an exo-directing strategy(2016-05) Ren, Zhi; Dong, Guangbin; Krische, Michael J.; Anslyn, Eric V.; Rose, Michael J.; Liu, Hung-Wen (Ben)Transition metal catalyzed functionalization of carbon-hydrogen bonds (C−H bonds) has become an exponentially growing field. Particularly, Pd-catalyzed methods with various directing groups (DGs) have been developed for site selectivity. In addition, the use of an oxime as a DG proved to be an efficient and removable DG. However, alcohol-based directing strategies are still rare and underdeveloped. The research and development in this dissertation mainly focused on the utilization of masked alcohols as DGs for late stage diversification. With an exo-directing strategy, the syntheses of chemically differentiated vicinal diols and 2-hydroxyalkylphenol derivatives were achieved. Through a series of studies on cyclopalladation of methine groups, the first direct C−H activation complex was prepared and characterized. Additionally, a comprehensive introduction of TM-catalyzed alkylation of aromatic C−H bonds with simple olefins was illustrated.Item Strong Bond Activation with Late Transition-Metal Pincer Complexes as a Foundation for Potential Catalysis(2012-07-16) Zhu, YanjunStrong bond activation mediated by pincer ligated transiton-metal complexes has been the subject of intense study in recent years, due to its potential involvement in catalytic transformations. This dissertation has focused on the net heterolytic cleavage of B-H and B-B bonds across the N-Pd bond in a cationic (PNP)Pd fragment, the C-H oxidative addition to a (PNP)Ir center and the recent results on the C-H and C-O oxidative addition in reactions of aryl carboxylates with the (PNP)Rh fragment. Transition metal carbene and carbyne complexes are of great interest because of their role in a wide variety of catalytic reactions. Our work has resulted in the isolation of a rhodium(I) difluorocarbene. Reaction of the rhodium difluorocarbene complex with a silylium salt led to the C-F bond cleavage and the formation of a terminal fluorocarbyne complex. Reductive elimination is a critical step of cross coupling reactions. In order to examine the effect of the pincer ligand on the reductive elimination reactions from Rh(III), the first pi-accepting PNP ligand bearing pyrrolyl substituents was prepared and installed onto the rhodium center. Arylhalide (halide = Br, I) oxidative addition was achieved in the presence of donor ligands such as acetonitrile to form stable six-coordinate Rh(III) compounds. The C-O reductive elimination reactions in this system were also explored.