Oxaziridines, ring opening

Cu(I)-Cu(II) Catalysis Radical Reactions Triggered by Oxaziridine Ring Opening... 

In a variant of this type of reaction in the diazepine system, the oxaziridine ring-opening was followed by reaction of the iminal that led to the destruction of the heterocyclic ring ... 

The oxaziridine ring itself is stable towards alkali there is, for instance, no substitutive ring opening by hydroxyl ions as in oxiranes. 2-r-Butyl-3-phenyloxaziridine (56) is not attacked by methoxide ion in methanol during 12 h at room temperature 3-isopropyl-2-r-octyloxaziridine does not react at room temperature with either solid potassium hydroxide or potassium methoxide solution (57JA5739). 

Action of catalytic amounts of vanadium compounds on oxaziridine (52) yields caprolactam almost quantitatively. Reductive opening of the oxaziridine ring and /3-scission yield radical (118), which recyclizes with elimination of the metal ion to form the lactam (63) (77JPR274). 

The outcome of this reaction can be rationalized by oxygen transfer from a transient intermediate (118 or an oxaziridine) to 1,3-DIBF [but see 89H(29)263]. Trapping of acylnitroso compounds yields similar products [81 JCS(P1)3250]. A similar ring-opening reaction has been observed when diarylalkylidencyclopropenes were reacted with 1,3-DIBF (93TL3131). Without citing [89H(29)263] C Moinet and co-workers reported a... 

Fig. 71 Radical reactions triggered by reductive ring opening of oxaziridines...

The use of the optically active (camphorylsulphonyl)oxaziridine did not afford enantioselectivity. A possible explanation for this lack of stereocontrol lies in the mechanism proposed (Scheme 56). It involves formation of an a-amino epoxide, its nucleophilic ring opening and either loss of a proton (route a) or hydrolysis (route b) (Scheme 56). 

Ring-Opening Cyclization of 2-(3-Alkenyl)aziridines and 3-(3-Alkenyl)oxaziridines... 

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