Benzylic quaternary centers are important motifs in organic active pharmaceutical ingredients, agrochemicals, and materials. I have developed three new reaction methods empowered by the attachment of a benzylic quaternary center to a C=C or C=O bond. I first developed a geminal-dialkyl-enabled acid-catalyzed intramolecular alkene hydrophenylation reaction to access five-membered rings (specifically indanes). In the course of this study, I discovered that, when using indoles instead of phenyl rings, the geminal-dialkyl group induces stabilizing intramolecular dispersive aromatic interactions, which facilitates stereospecific catalytic hydroindolation to form six-membered rings (affording tetrahydrobenzo[cd]indoles) in preference to five-membered rings. Lastly, I discovered, developed, and studied a room temperature tert-butoxide mediated decarbonylation of α-quaternary homobenzaldehydes, which is significantly more efficient than existing decarbonylations.