Onium ylides , including sulfur , oxonium and ammonium, are common intermediates employed in the syntheses of complex molecules. They are typically generated from the reaction of a heteroatom with a metal-supported carbene to furnish reactive zwitterionic intermediates that engage in a diverse set of reaction pathways, including 1,2-Stevens rearrangements, 2,3-sigmatropic rearrangements, and NH insertion reactions (Scheme 1A). The aziridinium ylides 10 represent a unique subclass of ammonium ylides whose reactivity is both poorly understood and underexplored, despite the potential for these reactive species to serve as key intermediates in the transformation of simple precursors to densely functionalized, stereochemically rich N-heterocycles. We are interested in applying the ability to shuttle aziridinium ylides along divergent pathways to explore diverse new amine chemical space, particularly in the context of using our new methods for the preparation of DNA-encoded libraries (DEL) to explore their potential bioactivity. Manipulating the reactivity of aziridinium ylides to achieve a desired reaction outcome can be challenging as compared to their acyclic ammonium counterparts. Aziridinium ylides are embedded in a highly strained ring, where the bonding constraints of the aziridine increase the energy required for pyramidal inversion of the nitrogen; often this rate is slow enough to measure using variable temperature (VT) or dynamic NMR spectroscopy. The presence of two invertomers hinders the ability to selectively form and engage aziridinium ylides in secondary reactions and has limited their applications in the synthesis of complex N-heterocycles. For example, in 2001 and 2004 respectively, Clark and Rowlands observed intramolecular [2,3]-Stevens rearrangements of aziridinium ylides to deliver dehydropiperidines in low 21-24% yields (Scheme 1B). In the former case, the low yield was attributed to the instability of the starting material which decomposed in one day when stored under argon at -30 ˚C. In Rowland's work, the alkyl aziridine substrate existed as two N-invertomers a and b in a ratio of 3:4, with an estimated barrier to N-inversion at room temperature of ~16-20 kcal/mol. Only a possessed the required geometry for the desired rearrangement; as a result, the major invertomer b underwent an unproductive 1,5-hydride shift at a faster rate than N-inversion to generate the invertomer required for the desired reactivity. In addition to the formation of invertomers of the aziridinium ylide, competitive cheletropic extrusion renders the use of these intermediates in selective transformations particularly challenging. Scheme 1. Prior work in aziridinium ylide chemistry and new divergent reactivity.