Controlling Site-Selectivity in Palladium and Platinum-Catalyzed C-H Arylation Reactions And A Novel Method to Prepare Aryl Sulfides from Thioethers.

In recent years, there has been an increased focus on developing transition-metal catalyzed reactions to directly functionalize carbon-hydrogen bonds. Specifically, efficient C-H arylation reactions to enable the rapid and green synthesis of biaryl molecules, which are useful as pharmaceuticals, materials, dyes, and agrochemicals, are highly sought after. The majority of this dissertation focuses on site-selective C-H arylation reactions. First, an example of the substrate-controlled arylation of pyrroles with diaryliodonium salts is presented. The site-selectivity of this reaction was found to be dictated by the sterics of the pyrrole starting material. Next, the palladium-mediated oxidative cross-coupling of benzo[h]quinoline and 1,3-dimethoxybenzene was studied computationally and experimentally to determine why different anionic ligands provide complementary selectivity on the simple arene substrate. It was determined that a change in rate-determining step when acetate or carbonate was the anionic ligand led to the observed selectivities. A catalytic variant was also developed that shows the same selectivity-determining factors. Finally, the first intermolecular PtII/IV-catalyzed direct C-H arylation of simple arenes with diaryliodonium salts is presented. For this system, the substrate scope and selectivity are defined and mechanistic studies providing evidence that the rate- and selectivity-determining step for this platinum-catalyzed reaction is reductive elimination are reported. This selectivity is complementary to the analogous palladium-catalyzed system in which oxidative addition is rate- and selectivity-determining and the opposite selectivity is observed upon reaction with naphthalene. The last chapter of this dissertation discusses the metal-free coupling of diaryliodonium salts and thiols or alkyl thioethers, a reaction which was discovered during the optimization of the platinum-catalyzed C-H arylation reaction. This transformation provides complementary reaction conditions and substrate scope to known methods and allows for easy and green access to aryl sulfides, which are useful for pharmaceutical and materials applications.PhDChemistryUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/108897/1/awags_1.pd