Oxaziridine synthesis peracids

Oxaziridines bearing no substituent at nitre en were not, until recently, prepared by the peracid procedure. They became available only after the discovery of a novel oxaziridine synthesis, which instead of formally adding oxygen to a C=N double bond consisted in adding an imino group to a C=0 double bond. The first compound of this type was prepared by Schmitz and Ohme ° in 1961 by treating cyclohexanone with an alkaline solution of hydroxylamine-O-sulfonic acid. S,3-Pentamethyleneoxaziridine (34) was formed (ca. 50% yield) in an extremely fast reaction. Analogous compounds were prepared from methyl ethyl ketone and benzaldehyde (yields ca. 30%). 

In 1976, the synthesis of oxaziridininm salt 66 was reported by Lusinchi and coworkers (Fig. 23) [128-130]. Salt 66 was obtained by either methylation of the corresponding oxaziridine with FSO Me or oxidation of the corresponding iminium salt with peracid. Subsequently, Hanquet and coworkers prepared oxaziridininm salt 67 by methylation of the corresponding oxaziridine with Meerwein s salt (MejO BF ") or oxidation of the A -methyl isoquinoUnium fluoroborate salt with peracid [131, 132],... 

Peracetic acid was later replaced by m-chloroperbenzoic acid (MCPBA), which is easier to handle and relatively more stable than peracetic acid. Other solid per-acids including chiral peracids have been used in the synthesis of chiral oxaziridines (see Section IIl.l). Recently, MCPBA has been found to be effective in the preparation of oxaziridines with no substituent on the ring nitrogen, a class of oxaziridines that are rather unstable (Ref. 13 and references cited therein). Phase-transfer catalysis has been employed in an improved synthesis of Msulfonyloxa-ziridines. p-Nitroperbenzoic acid was used to oxidize an epoxy imine to an epoxyoxaziridine. ... 

The rapid development of chiral phosphine derivatives of ferrocene was undoubtedly due to their application in catalysis. In contrast, chiral sulfur compounds from lithiated iV,iV-dimethyl-l-ferrocenylethylamine were only prepared about 15 years later [140], For the synthesis of such derivatives, the lithiated amine is treated with disulfides as shown in Fig. 4-24, top (and analogously, diselenides [141]). The sulfides obtained are easily oxidized by peracids or NaI04 to the corresponding sulfoxides. As sulfur becomes a new center of chirality by the oxidation, diastereoisomeric sulfoxides are formed in ratios depending on the oxidant [140]. If chiral oxaziridines [106, 142] are used as oxidizing agents, the diastereoisomeric ratio is appreciably... 

The synthesis of oxaziridines from Schiff bases and peracids, as reported by Krimm, ° Emmons, and Horner and Jurgens, is still the most popular procedure for their preparation [Eq. (1)]. 

One can oxidize N-sulfonyl imines to the corresponding oxaziridines using oxidants such as a peracid or oxone [5 b, 93,94], Thus, Davis and coworkers have developed a biphasic procedure for converting imine 278 to frans-oxaziridine 279, in high yield [5b] [Eq. (65)]. Similarly, camphor-derived N-sulfonyl imines 277 and 268 can be oxidized to the endo oxaziridines 280 and 281, respectively [92,93] [Eq. (66), (67)]. Davis and others have now demonstrated the exceptional utility of oxaziridines as oxidants in organic synthesis and, in particular, the value of camphor-derived reagents, such as 280 and 281, in asymmetric synthesis [94,95],... 

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