Mechanistic study is presented as a central tool for the development of new, selective catalytic reactions. Two case studies are discussed. The first study highlights the development of quinone-based catalysts for the aerobic dehydrogenation of N-heterocycles. Inspired by quinone cofactors found in amine oxidase enzymes, this work identifies a new, abiological mechanism for substrate oxidation that proves critical for good catalytic efficiency and broad reaction scope. The second study highlights an enantioselective unimolecular substitution (SN1) reaction for the construction of quaternary stereogenic centers. A dual catalyst system is identified which is capable of generating – and controlling – highly electrophilic tertiary cations as reactive intermediates. Detailed mechanistic analysis supports a stepwise, stereoablative substitution pathway.