Organocatalytic nitrogen transfer to unactivated olefins via transient oxaziridines

Aldehyde-catalyzed epoxidation of unactivated alkenes with aqueous hydrogen peroxide

“…Furthermore, control experiments without catalyst, oxidant, buffer or MeCN confirmed that all components are necessary for the epoxidation ( Table 1 , entry 3–6). In agreement with our previous findings, 20 a ,20 b a lower pH provided the desired product in compromised yield, validating that pH = 11 is ideal for the generation of Payne's intermediate 20 b ,21 (peroxycarboximidic acid V from MeCN and H 2 O 2 , Table 1 , entry 7 and mechanism in Scheme 5 ). The importance of the generation of Payne's intermediate for the success of our protocol is also highlighted by the fact that in the absence of MeCN, no epoxidation is taking place ( Table 1 , entry 6).…”

Fe(II)‐Catalyzed Synthesis of Unactivated Aziridines (N‐H/N‐Me) from Olefins Using O‐Arylsulfonyl Hydroxylamines

“…These limitations could be largely addressed later through the methods developed by Kurti, [7a] Falck, [7c] and our lab [7b] utilizing hydroxylamine‐O‐sulfonic acid (HOSA) and O ‐(mesitylsulfonyl)hydroxylamine (MSH) as the aminating agents (Scheme 1a). Recently, the group of Kurti reported an effective organocatalytic aziridination of unactivated olefins via transient oxaziridines generated from ethyltrifluoropyruvate in the presence of HOSA:Cs 2 CO 3 in hexafluoroisopropanol (HFIP) [8] . Despite this progress, these methods have one or the other limitations like the requirement of expensive metal catalyst [Rh 2 (esp) 2 , US$ 267/500 mg], additives (pyridine, cesium carbonate, ligands), relatively costly HFIP as the solvent, longer reaction time, and low reactivity for terminal and conjugated alkenes, etc.…”

“…Recently, the group of Kurti reported an effective organocatalytic aziridination of unactivated olefins via transient oxaziridines generated from ethyltrifluoropyruvate in the presence of HOSA:Cs 2 CO 3 in hexafluoroisopropanol (HFIP). [8] Despite this progress, these methods have one or the other limitations like the requirement of expensive metal catalyst [Rh 2 (esp) 2 , US$ 267/500 mg], additives (pyridine, cesium carbonate, ligands), relatively costly HFIP as the solvent, longer reaction time, and low reactivity for terminal and conjugated alkenes, etc. Therefore, any method that replaces the expensive catalyst and solvent with an economical, non-toxic and readily available catalyst and solvent is highly desired.…”

Electrophilic Aminating Agents in Total Synthesis

“…[350] More recently,ametal-free alkene aziridination was reported, wherein unprotected aziridines were generated using an oxaziridine intermediate (Scheme 29). [351] This reactive species was generated in situ from an electron-poor ketone organocatalyst and ahydroxylamine-based aminating agent (HOSA). Themethod allows the stereospecific aziridination of unactivated, nonconjugated olefins,a nd can be thought of as an aza analogue of the Shi epoxidation.…”