Swern reagent

Oxidation of amines to imines.1 This Swern reagent effects oxidation of ben-zylamines to the corresponding Schiff bases in 40-60% yield. It also oxidizes in-doline to indole in 88% yield. 

Oxidation. DMSO activated by P205 (1 equiv.) and in combination with triethylamine is useful for oxidation of alcohols to ketones and aldehydes, particularly in cases where the Swern reagent results in chlorinated byproducts. Yields are typically 80-85%. 

The samarium diiodide-mediated reductive cyclization of a sugar-derived oxime ether provides a trace amount of an unexpected cyclized product <1997JOC7397>. It is thought that its formation probably arises from an intermediate (methylthio)methyl ether formed with the excess of Swern reagent used to generate the aldehyde in situ after cyclization (Equation 59). 

Although an oxidation with Swern reagent gives a better yield, an oxidation with PDC is preferred because it is easier to carry out. Swern oxidation produces ketone contaminated with sulfur-containing impurities, which may interfere with a subsequent hydrogenation. 

The purposeful simultaneous oxidation of a secondary alcohol and dehydration of a tertiary alcohol is brought about by the use of excess of Swern reagent. ... 

The Swern reagent is also generally superior for oxidation of /3-hydroxy esters to /I- keto esters (50-90% yield). 

Oxidation of alkyl trimethyl- and triethylsilyl ethers, ROSi(CH3)3 or ROSi-(C2H5)3.1 Silyl ethers of this type can be oxidized directly to carbonyl compounds by the Swern reagent. This oxidation provides an efficient route to the Corey aldehyde (2). 

Dehydrogenation of diaziridines.2 The Swern reagent is more effective than Ag20 or NBS for oxidation of the diaziridines 1 to the diazirines 2, of interest because they are photolyzed to reactive carbenes. 

Oxidation of alcohols. Griffith and Ley1 report various improvements for use of this reagent for catalytic oxidation of alcohols in combination with N-methyl-morpholine N-oxide as reoxidant. In general, the yields with this oxidant are higher than those obtained by the Swern reagent. 

The symbol (0) denotes oxidation by one of the very general but ill-defined oxidizing agents from the laboratory of the famous Welsh chemist Owen Bracketts. Here the Swern reagents were the best (see Chapter 24). 

Oxalyl chloride-dimethyl sulfoxide (Swern reagent), 76, 112... 

Good results were obtained by oxidation of the /V-acylhydroxylamine derived from (/ )-methoxymandelic acid with the Swern reagent at — 78 "C in dichloromethane100. 

Alkyl-2//-aziridine-2-carboxylates 867 have been oxidized with the Swern reagent to afford 2//-azirine-2-carbox-ylates <1995TL4665>. Oxidation of either the (Z)- or the ( )- isomers of 867 provides the same 2//-azirine-2-carboxylate 868, where the integrity of the stereogenic center at C-2 is retained. This regioselectivity results from the unexpected removal of the apparently less acidic C-3 proton during the base-induced ty -elimination of the A-dimethylsulfonium intermediate (Scheme 217). 

Oxidation. This combination together with Et,N is comparable to the Swern reagent. 

Chlorodimethylsulfonium chloride (Swem reagent) represents another metal-free alternative for hydrazone oxidation [54]. The strategy was discovered by chance during research on a new conversion of free hydrazones to alkyl chlorides [159]. When benzophenone hydrazone was exposed to Swern reagent in the absence of an amine base, Brewer and laved observed localized yet transient red coloration of the reaction mixture. Diligent experimentation then led to the... 

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