Formation d'un sel d'oxaziridinium quaternaire par methylation d'un oxaziranne - mise en evidence de ses proprieties oxydantes

Binaphthalene‐Derived Iminium Salt Catalysts for Highly Enantioselective Asymmetric Epoxidation

“…Initially, enantiomeric excesses when employing enantiomerically pure oxaziridinium salts, for example 2 , ranged from low to moderate 3–5. Our own approach to chiral iminium salt catalysts, which has led to several systems that afford epoxides with >90 % ee ,6,7d differs from previous investigations, where the exocyclic group attached to the nitrogen atom of the iminium salt has invariably been methyl or ethyl.…”

“…Enantiomerically enriched epoxides have found many applications in asymmetric synthesis,1 and development of efficient catalysts for asymmetric epoxidation has received considerable attention 2. Oxaziridinium salts such as 1 , generated from iminium salts and a stoichiometric oxidant, typically Oxone, are strong electrophilic oxidants for olefin epoxidation,3 and have the advantage that they are “organocatalysts,” no metal species being involved in the catalysed reaction. …”

Recent Advances in the Catalytic Asymmetric Reactions of Oxaziridines

“…A series of nucleophiles that include sulfides [ 22 ], sulfoxides, alkenes [ 23 ], thiolates [ 24 ], phenols [ 25 , 26 ], naphthols, enolates, silyl enol ethers, selenides [ 27 ] and C-H bonds [ 28 , 29 , 30 , 31 ] could be oxidized via an asynchronous transition state in which N-O bond cleavage is faster than C-O bond cleavage ( Figure 2 ) [ 10 ]. Oxaziridinium salt 5 , first discovered by Lusinchi and co-workers in 1976 [ 32 , 33 ], was generated by the oxidation of the corresponding iminium salt with peracid or monoperoxysulfate. It exhibits a special oxidizing power derived from the strongly electrophilic oxygen atom.…”

Organocatalytic Asymmetric Oxidations with Hydrogen Peroxide and Molecular Oxygen

“…The asymmetric epoxidation of unfunctionalized alkenes has been performed by employing chiral oxaziridinium salts, as first illustrated by the work of Lusinchi et al 53. After this report, different chiral iminium salts were synthesized as suitable precursors for the formation of the postulated oxaziridinium species in the presence of Oxone as the stoichiometric oxidant 54.…”