Synthesis of Boron, Silicon, and Phosphorus Lewis Acids and Frustrated Lewis Pair Complexes for C=O and C-F Bond Activations

The recent proliferation of main group catalysts and stoichiometric reagents useful in effecting transformations of organic molecules has been augmented by development of the chemistry of frustrated Lewis pairs (FLPs). In seeking to both complement and emulate the reactivity of transition metal catalysts, both the synthesis of new Lewis acids and FLPs and the discovery of new reactivity with organic substrates has been explored. Boron Lewis acids such as B(C6F5)3 and electrophilic borenium cations are among the most commonly employed main group catalysts, particularly for the hydrogenation of unsaturated bonds. The first chapter of this thesis details explorations in modulating the Lewis acidity of neutral and cationic boron electrophiles by tuning phosphinimine and phosphine-amine ligands. A family of compounds featuring a P-N-B motif are presented. In seeking to broaden the range of main group catalysts, phosphorus Lewis acids have been explored. The third and fourth chapters presented herein detail the synthesis and catalytic activity of electrophilic phosphonium cations (EPCs). Synthesis of a chloride-substituted dication, and ferrocenyl-based mono- and dications are described, with a particular emphasis on their catalytic activity in the deoxygenation of ketones. The fifth chapter details the synthesis of phosphorus cations which attempt to model intermediates in EPC-mediated catalysis. Silylium cations are strongly fluorophilic and have previously been shown to cleave aliphatic C-F bonds. The final chapter presents examples of silylium cations in combination with weak phosphine Lewis bases for the selective cleavage of one C-F bond of an aryl-CF3 functionality. The FLP-captured PhCF2 is then converted to PhCF2H, completing a formal hydrodefluorination process of PhCF3 to PhCF2H. Analogous reactivity is observed with aryl-CF2 compounds.Ph.D

A Dual Sensor for Biogenic Amines and Oxygen Based on Genipin Immobilized in Edible Calcium Alginate Gel Beads

Food is often wasted due to real or perceived concerns about preservation and shelf life. Thus, precise, accurate and consumer-friendly methods of indicating whether food is safe for consumers are drawing great interest. The colorimetric sensing of biogenic amines released as food degrades is a potential way of determining the quality of the food. Herein, we report the use of genipin, a naturally occurring iridoid, as a dual colorimetric sensor for both oxygen and biogenic amines. Immobilization of genipin in edible calcium alginate beads demonstrates that it is a capable sensor for amine vapors and can be immobilized in a non-toxic, food-friendly matrix