Alcohols dimethyl sulfoxide-based reagents

The roles of the various reagents are as follows [1023] The activator converts dimethyl sulfoxide into a reactive sulfonium intermediate, which reacts with the alcohol and forms a complex A. A base, usually triethyl-amine, abstracts a proton from one of the methyl groups linked to sulfur. An intramolecular shift of electrons causes the disintegration of the com-... 

In more recent works, the use of dicyclohexylcarbodiimide has been abandoned because the reaction works satisfactorily with acid catalysts alone, followed by bases such as triethylamine or diisopropylethylamine, which gives, sometimes, even better yields than triethylamine [1012,1023. Several activators are being used, and the best seems to be oxalyl chloride (theSwern oxidation) [1023,1149]. Other activators are mentioned in the section Oxidation of Primary Alcohols to Aldehydes. The advantages of oxidations with dimethyl sulfoxide lie in the mildness of the reagent and in the low temperatures, sometimes -45 °C [1020] or -60 °C [1023], at which the reactions are run. 

Because of the toxicity of chromium-based reagents, other methods for the oxidation of alcohols have been developed. One of the most widely employed methods, called the Swem oxidation, uses dimethyl sulfoxide [(CH3)2SO], oxalyl chloride [(COCl)2], and triethylamine. Since the reaction is not carried out in an... 

This is a good point to introduce some of the organic applications of higher-valent sulfur compounds. Dimethyl sulfoxide (DMSO) is well known in this regard it is not only an important polar, aprotic solvent but is also used to oxidize primary and secondary alcohols to the corresponding carbonyl compounds in a number of synthetic reactions, of which the Swern oxidation is the most important. The reagents used in the Swern oxidation are DMSO, oxalyl chloride, and an organic base such as triethylamine ... 

Oxidations. WChlorosuccinimide-dimethyl sulfide (NCS-DMS) is one of several reagents for converting alcohols to alkoxydtmethylsulfonium salts, which in the presence of base convert to the corresponding carbonyl compounds via intramolecular proton transfer and loss of dimethyl sulfoxide. These oxidations are among the mildest and most selective for conversions of alcohols to aldehydes and ketones. This reaction does not suffer the overoxidation to acids or the carbon-carbon bond cleavages which are often encountered in chromium(VI) or manganese(VII) oxidations (eq 1). ... 

As an alternative to chromium-based oxidants, chemists have developed other reagents for oxidizing alcohols, several of which are based on chlorodimethylsulfonium ion [(CH3)2SC1 ]. Most commonly, chlorodimethylsulfonium ion is generated under the reaction conditions by the reaction of dimethyl sulfoxide with oxalyl chloride. 

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