In previous reports, many nitrogen-containing heterocycles can be aminated on nitrogen using HOSA as an aminating agent. 17 In 1957, Meuwsen and Gösl discovered that tertiary amines and heterocyclic amines, such as trimethylamine (Me3N), pyridine, and quinoline, could react with HOSA to yield N-aminated products through a proposed nitrene intermediate. 18 As part of an ongoing program aimed at exploring nitrene chemistry, 19 we envisioned whether olefin aziridination could be achieved in this reaction system. Drawing inspiration from Kürti's seminal work, we used (Z)-cyclooctene 1a as the model substrate and HOSA as the aminating agent. Table summarizes the results of the optimization study. Employing piperidine as the base in 1,1,1,3,3,3-Hexafluoroisopropanol (HFIP, 0.5 M) for 12 hours, giving the desired product 2 in 86% isolated yield (entry 1). Intriguingly, the introduction of metal catalysts such as Rh2(esp)2 and FeCl3 unexpectedly hindered the reaction (entries 2-3). Similarly, the addition of an electrondeficient ketone catalyst (ethyl trifluoropyruvate) produced comparable results (entry 4). Performing the reaction in the dark did not improve the yield, showing the insensitivity of the reaction to light (entry 5). Various bases such as pyridine, DMAP, Et3N, and DBU, cesium carbonate yielded the target product in moderate yields (55-70% yield, entries 6-10). Notably, the reaction did not proceed in the absence of base (entry 11). Replacing the solvent with trifluoroethanol (TFE) resulted in a reduced yield of 31% (entry 12), and other solvents, including methanol, toluene, dichloromethane, MeCN, THF, and water, failed to give the desired product (entry 13, see SI for more details). Additionally, the reaction displayed sensitivity to water, evidenced by a decrease in yield to 53% upon the addition of 10 equivalents of water (entry 14). 17 Lowering the reaction concentration had no discernible impact, while an increase in reaction concentration may be attributed to solubility issues with HOSA, leading to a reduced yield of 57% (entries 15-16). However, to our delight, increasing the equivalents of both HOSA and piperidine to 2.0 further enhanced the reaction yield to 97%. Furthermore, we also tried other types of aminating reagents, (aminooxy)diphenylphosphine oxide A1, and O- hydroxylamine A2 yielded the desired product in 78% and 50% yield, respectively. While the other aminating reagents A3-A5 failed to afford the desired aziridine compound. Next, with the optimized conditions in hand, the substrate scope of olefins was investigated. Generally, as shown in Scheme 2, mono-and di-substituted cyclic and linear olefins yielded aziridines in moderate to good yields, with electron-rich alkenes bearing more enhanced reactivity. For instance, aziridine 3 is produced in an 80% yield using cis-4-octene and piperidine as a base ([A]). However, olefins featuring the hydroxyl group (-OH) (4s, 6s) were incompatible under condition . Switching the base from piperidine to pyridine as the base affords the target products 4 and 6, in 41% and 54% yield, respectively. Additionally, protecting the hydroxyl group of 4s to tert-butyldimethylsilyl ether (-OTBS) (5s) did not lead to the desired product under either condition [A] or . Trans linear internal olefin 7s also gave product 7 in 42% yield. Terminal olefins, however, are less reactive and produce the target aziridines in relatively low yields (8-10). Subsequent investigations into cyclic olefins revealed that a majority of substrates efficiently gave the desired products. Notably, bridged cycloalkenes, such as norborene 13s, gave 13 in 74% yield with high stereoselectivity. Terpinen-4-ol (15s) under condition gaves the target product in 67% yield. However, further investigations into dienes and trienes reveal that they exhibit excellent regioselectivity regardless of the reactivity differences among the double bonds, leading exclusively to mono-aziridination products. For substrates containing multiple carbon-carbon double bonds, the reaction tends to occur specifically at the more electron-rich ones. For instance, diene 16s containing both terminal and internal olefins, the aziridination selectively occurred on the internal olefin in 93% yield under condition . Using Osthole 17s as a substrate specifically yielded product at the electronrich tri-substituted olefin site in moderate yield, while the conjugated internal olefin remained unreacted. Using (-)-Linalool as a parent substrate, when the hydroxyl group was masked by isobutyryl group (-COCHMe2), the expected aziridine 18 was achieved in 61% yield with 1.4:1 d.r. under condition [C], however, when using free (-)-Linalool 19s as substrate, the cascade product of aziridination followed by intramolecular nucleophilic ring-opening was obtained in 49% yield with 1:1 d.r. using pyridine as a base under condition .