Cycloadditions have long been held as the premier for economical constructions in organic synthesis, the use of which has led to the completion of innumerable total syntheses and methodologies. Towards this end, the Rawal group has a long-standing interest in cycloaddition methodologies and applications in total synthesis. This thesis details the exploration of a novel approach to cyclohepta[b] indoles via a [4+3] cycloaddition reaction of 3-alkenyl indoles and stabilized oxyallyl cations. The transformation was explored fully, and a catalytic, enantioselective approach via highly acidic imidodiphosphorimidates (IDPi) was discovered and used to showcase a general enantioselective [4+3] cycloaddition reaction of stabilized oxyallyl cations. Finally, a novel approach towards the ambiguine alkaloids has been explored, and significant progress towards amibiguine Q has been made. Additionally, through the use of our novel [4+3] cycloaddition methodology, a generalizable route towards pentacyclic ambiguines has been achieved.