Vicinal diamines (1,2-diamines) are well-represented in molecules of value, including those used as medicines, ligands, and agrochemicals. Given their importance to multiple areas of synthetic chemistry, it is no surprise that numerous protocols have been invented for their construction. Diamination of olefins and untethered (intermolecular) aminolysis of aziridines are common strategies for accessing these motifs (Scheme 1). The direct diamination of olefins is a powerful approach for the construction of vicinal diamines, as it installs both nitrogens in a single synthetic step; some limitations of existing protocols include harsh reaction conditions, limited substrate scope, and issues with regioselectivity and stereoselectivity. Intermolecular aminolysis of aziridines has also been studied in numerous contexts, but, depending on the substrate and reaction conditions, intractable mixtures of regioisomeric products can result. In contrast to the first two approaches, aminolysis of aziridines utilizing detachable tethers has hardly been explored for the synthesis of 1,2-diamines (Scheme 1). As part of a larger program on olefin-functionalization and ringopening of aziridines and epoxides, our laboratory is very interested in using sulfamate tethers as convenient N-nucleophiles. Here, we present a mild protocol for the intramolecular ring opening of aziridines by pendant sulfamates, which allows for regioselective and stereospecific syntheses of a variety of vicinal diamines. Further, we demonstrate that the product oxathiazinanes are convenient synthons for an array of polyfunctional targets.