Oxaziridine Oxidations

The mechanism of oxygen transfer from oxaziridines to nucleophiles is believed to involve an Sn2 type reaction and this assumption is supported by theoretical and experimental studies. When sulfides are oxidized to the corresponding sulfoxides and sulfones, the molecular recognition is steric in origin, and it is determined by the substituents on both the substrate and the oxaziridine. For the oxidation of enolates, the molecular recognition is explained with an Sn2 mechanism as well as by an open (non-chelated) transition state where the nonbonded interactions are minimized. The mechanism of oxygen transfer to an enolate to form the corresponding acyloin is shown below.  

During the highly stereoselective total synthesis of epothilone B by J.D. White and co-workers, the stereochemistry of the alcohol portion of the macrolactone was established by applying Davis oxaziridine oxidation of a sodium enolate. The sodium enolate was generated from the corresponding chiral oxazolidinone derivative, which upon oxidation gave 71% yield of a-hydroxylated compound. 

An abbreviated synthesis of a substituted 1,7-dioxaspiro[5.5]undec-3-ene system constituting the C3-C14 portion of okadaic acid was developed in the laboratory of C.J. Forsyth. The C3-C8 fragment, a substituted valerolactone, was prepared in three steps. The diastereoselective a-hydroxylation of this lactone was accomplished by using Davis chirai camphorsuiphonyi oxaziridine on the corresponding lithium enolate at -78 °C. The isolated yield was 61% and the ratio of diastereomers was 10 1. 

The first total synthesis of (-)-fumiquinazoline A and B was accomplished by B.B. Snider and co-workers using a Buchwald-Hartwig Pd-catalyzed cyclization of an iodoindole carbamate to construct the imidazoindolone moiety. In order to set up the stereochemistry at the benzylic position of the indole fragment, the double bond was oxidized with the saccharine-derived Davis oxaziridine in the presence of methanol to give the major diastereomer in 65% yield. 

The mechanism of the enone-aikene [2+2] photocycloaddition presumably follows the scheme below. Upon irradiation 1) a triplet exciplex is irreversibly formed from the triplet enone and ground state alkene 2) the triplet exciplex collapses to one or more 1,4-biradicals. 3) the biradicals either cyclize to the cyclobutane or revert to starting materials and 4) the biradical reversion decreases the overall efficiency of the process. 

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Oxaziridines oxidize sulfides to sulfoxides. Again, the A -sulfonyl derivatives seem to be the best oxidizing agents. They react with sulfides at room temperature to produce sulfoxides uncontaminated with sulfones chiral oxaziridines produce chiral sulfoxides. In addition, chiral thiolsulfinates can be obtained from... 

Davis oxaziridine oxidation Oxidation of electron-rich substrates (e.g. alkenes, enolates, enol ethers etc.) with oxaziridines. 130... 

Related reactions Davis oxaziridine oxidation, Prilezhaev reaction, Sharpless asymmetric epoxidation, Shi asymmetric epoxidation ... 

Davis and coworkers [506, 744] performed the asymmetric oxidation of pro-chiral sulfides with chiral oxaziridines, and reagents bearing the bomane skeleton 2.82 or 2.83 (X = Cl) were the most efficient. The chiral oxaziridine oxidations are... 

Oxidation of simple thietans with peroxy-acids gives monoxides and dioxides.However, oxidation of tetraphenyl-2-thietanone (89) with m-chloroperoxybenzoic acid gives (90), which is a stable carboxylic-sulphinic acid anhydride. Thietan dioxides are formed in the oxidation of thietans by NaMn04. 2-Arylsulphonyl-3-aryl-oxaziridines oxidize sulphides (including thietans) to sulphoxides. 3-Hydroxythietan can be oxidized to 3-thietanone, without oxidation at sulphur, with DMSO and benzoic anhydride. ... 

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