Chlorodimethylsulfonium chloride

DMSO and oxalyl chloride react in an explosive manner at room temperature. The reaction at -60°C is almost instantaneous, resulting in a copious evolution of carbon monoxide and carbon dioxide. As soon as, a drop of a solution of DMSO in CH2C12 contacts a solution of oxalyl chloride in CH2C12 at -60°C, an almost instantaneous reaction takes place, resulting in the formation of chlorodimethylsulfonium chloride (30). 

Thus, Corey and Kim explained in 1972248 that reaction of dimethyl sulfide with chlorine yields chlorodimethylsulfonium chloride, which is precisely the same species described later249 as the activated DMSO species, generated during a Swern oxidation. 

Chloroacetaldehyde oxime, 2-carbon cyclization using, 55, 287 N-Chloroamides, chlorinating agents for pyrroles, 57, 326 N-Chloroamines radical cyclizations from, 58, 19 radicals by photolysis of, 58, 10 Chlorocarbonylsulfenyl chloride, reaction with 5-aminouracils, 55, 153 Chlorodimethylsulfonium chloride,... 

In the Swern oxidation, the reaction of oxalyl chloride with DMSO may generate chlorodimethylsulfonium chloride (A), which reacts with the alcohol to give alkoxysulfonium ion intermediate B. The base, typically triethylamine, deprotonates the alkoxysulfonium ion B to give the sulfur ylide C, which decomposes to give DMS and the desired aldehyde or ketone (Scheme 7.7). The temperature of this reaction is kept near —60 to -78°C. 

Chlorodimethylsulfonium chloride (generated from chlorine and dimethyl sulfide) can be used in the same way for preparation of a-chloro ketones. 

Methylthiomethyl esters have been prepared by reaction of triethylammonium salts of carboxylic acids with chlorodimethylsulfonium chloride or by reaction of the potassium salts of carboxylic acids with chloromethyl methyl sulfide in the presence of sodium iodide and 18-crown-6. ... 

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... 

Step 1 The alcohol reacts with the active oxidizing agent, chlorodimethylsulfonium ion, previously generated by the reaction between dimethyl sulfoxide and oxalyl chloride. The oxygen of the alcohol displaces chloride from sulfur. 

DMSO and oxalyl chloride react to form a chlorodimethylsulfonium salt. 

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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