Camphor imine, oxidation

The Schmitz reaction can be unsuccessful in sterically demanding environments in such circumstances, the electrophilic aminating agent reacts faster with ammonia than with hindered ketones <1965JA2665>. Consequently, the synthesis of 2-azi-camphane 64, a compound which is unobtainable under standard conditions <1996TL6647>, was achieved by slow diaziridination of camphor imine hydrochloride 63 (rather than camphor itself) with hydroxylamine-O-sulfonic acid (HOSA)-ammonia, followed by iodine-mediated oxidation (Scheme 22) <2001S379>. 

The oxidation of imines continues to be the most common method for the preparation of oxaziridines. Page et al. recently described the preparation of enantiomerically pure chiral NH-oxaziridines derived from camphor and fenchone <2000JOC4204>. Treatment of camphor imine 303 with 1 equiv of MCPBA at —30 to —40°C in dichloromethane gave NH-oxaziridine 50 in 94% yield. The fenchone-derived oxaziridine 305 was obtained similarly... 

Related reagents 2.83, obtained from camphor imine, are usefid for asymmetric oxidation of sulfides and selenides to chiral sulfoxides and selenoxides [S06, 749]. To obtain high enantioselectivities, the substituents on the sulfur or selenium must be of a sufficiently different size. 

The oxidation of imines derived from substituted cyclohexanones occurs predominantly from the equatorial direction. However, the product oxaziridines can undergo subsequent equilibration to favor a more stable conformation which places the bulkier nitrogen substituent in an equatorial conformation (Scheme 24). A particularly useful oxaziridine derived from camphor was formed exclusively via exo approach of the reagent (equation 42). ... 

Nitrosolysis of camphor ethyl acetal with ethanolic ethyl nitrite in sulphur dioxide yields the orthoester oxime (205) which is rapidly dehydrated by excess acetal to the orthoester nitrile which then reacts with sulphur dioxide to form the ester nitrile and diethyl sulphite.Further papers in this section include the full paper on ozonolysis of silyl ethers (Vol. 5, p. 33), another synthesis of camphor-enol trimethylsilyl ether (cf. Vol. 6, p. 41)/°° the conversion of camphor oxime with Grignard reagents into the corresponding imine with no aziridine formation/° the preparation of (206) by treating bornylene with trichloroacetyl isocyanate/ the oxidation of thiocam-phor to the 5-oxide and alkylation in the presence of thallium(i) ethoxide to a/S-unsaturated sulphoxides/ and the free-radical C-3 alkylation of camphor with alkenes. " ... 

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],... 

Oxaziridines, prepared by the oxidation of imines, are selective oxygen-transfer reagents. In particular, the camphor-derived reagent is widely nsed for enantioselective oxygenation of enolates and other nucleophiles. 

Starting with (5)-1 -phenylethyl amine, a chiral sulfonyloxaziridine has been prepared by A,T-sul-fonylation and subsequent formation of an imine with an aromatic aldehyde (best example pentafluorobenzaldehyde). Oxidation leads to a 1 1 mixture of diastereomeric oxaziridines 77 which can be separated by HPLC76. The compounds behave similarly to the chiral camphor-derived sulfonyloxaziridines, as they are able to epoxidize alkenes not containing special functional groups with some enantioselectivity (Section D.4.5.2.1.). Another attractive starting material is cheap commercial saccharin. Reaction with alkyl- or aryllithium compounds leads to addition... 

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