Sulfur-stabilized reagents

Sulfation is defined as any process of introducing an SO group into an organic compound to produce the characteristic C—OSO configuration. Typically, sulfation of alcohols utilizes chlorosulfuric acid or sulfur trioxide reagents. Unlike the sulfonates, which show remarkable stability even after prolonged heat, sulfated products are unstable toward acid hydrolysis. Hence, alcohol sulfuric esters are immediately neutralized after sulfation in order to preserve a high sulfation yield. 

TABLE 4. Generation of sulfur-stabilized anion with organometaUic reagents... 

Sulfur-stabilized copper-zinc carbanions have been used [299] by Knochel et at A first type obtained from the reaction of the Simmons-Smith reagent with a copper(i) thiolate was treated with a... 

From oxidative cleavage of 1,2-diols and 1,2-amino alcohols Dibutyltin oxide, 95 By reaction of alkyl halides with sulfur-stabilized carbanions Methylthiomethyl p-tolyl sulfone, 192 From reduction of carboxylic acids Vilsmeier reagent, 341 From terminal alkenes by addition reactions... 

D. Dichromate-Sulfuric Acid Reagent is prepd by dissolving 0.5g of K2Cr207 in 100ml of 60% sulfuric acid. It was proposed by Oven-ston for use in chromatographic analysis of propints, for the location of substituted ureas and urethanes which have been employed as stabilizers and plasticizers(Ref 18a)... 

The stereocontrolled synthesis of functionalized lactams has been achieved via sulfur-stabilized enolates.36 Thio-substituted enolates were the reagents of choice as these proved to be more generally applicable than the corresponding sulfoxide-substituted enolates. 

Alkyllithium reagents also yielded the corresponding alkylated sulfur-stabilized allenyl anions. Thus, treatment of 286 with -BuLi gave the lithio derivative 287 which was reacted with the aldehyde 288. Upon acidification with trifluoroacetic acid (TEA), the furan-containing diester 289 was obtained in 67% yield (Scheme 36) <2002CC2824>. 

Review. Seebach and Corey have published a general paper on the preparation and metalation of 1,3-dithianes and examples of the reaction of 2-lithio-l,3-dithianes with electrophilic reagents (alkyl halides, carbonyl compounds, acids, and oxides). The value of these sulfur-stabilized anionic reagents is that they are equivalent to acyl anions (a), in which the normal polarity of the carbonyl group is reversed (reversible umpolung). 

In both cases, sulfur stabilized the lithium derivative and reaction with alkyl halides proceeded in a manner analogous to other vinyllithium reagents. Hydrolysis required mercuric salts or another Lewis acid to give the ketone, as in the preparation of Ph2CHCOMe from 367. Another preparation involves direct treatment of an... 

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