Sulfones elimination

The Pd-catalyzed BCR cycloaddition is highly diastereoselective. For example, exclusive addition at the least-hindered face of the 5-oxaeneone (102) is observed (equation 113). Similarly, the six-mem-bered ring sulfone (103) also gives essentially a single adduct (104). This compound can be readily transformed, via ozonolysis and sulfone elimination, to a bicyclic enone that is equivalent to a cyclopen-... 

Fluoride also has a high affinity for tin and the analogous P-stannyl sulfone elimination is an efficient and fast reaction. The requisite P-stannyl sulfones are prepared by alkylation of the sulfone anions as in the silicon case however, the iodoalkylstannanes react faster [relative rate order MesSiCH (1),... 

Aromatic nitro compounds and sulfonates elimination of nitrite or sulfite by dioxygenation (Sections 6.8.1 and 6.8.2)... 

Successful four-fold sulfone eliminations also led to the p-xylylene analogue 183 and the flattened o-xylylene bridged hydrocarbon 184 (Scheme 23). Hydrocarbon 183 has a cupped arrangement of rings, evident from the appearance of the H2- resonance at 56.59, a signal that is absent in the spectrum of 183-D, The... 

Related to these reactions is the oxidation of alkyl halides or tosylates to carbonyl compounds with dimethyl sulfoxide (or trimethylammonium A/-oxide). The reaction is effected simply by warming the halide (normally the iodide) or sulfonate in DMSO (or MeaNO), generally in the presence of a proton acceptor such as sodium hydrogen carbonate or a tertiary amine. Oxidation never proceeds beyond the carbonyl stage and other functional groups are unaffected. The reaction has been applied to benzyl halides, phenacyl halides, primary sulfonates and iodides and a limited number of secondary sulfonates. With substrates containing a secondary rather than primary halide or sulfonate elimination becomes an important side reaction and the oxidation is less useful with such compounds. 

Diels-Alder reaction, catalyzes the cycloaddition between terachlorothiophene dioxide and iV-ethylmaleimide. This reaction occurs via a bridged sulfone intermediate forming tetrachlorophthalimide through sulfone elimination and spontaneously oxidative aromatization (Fig. 3B). This catalyst displays an effective molarity (EM=kca/ku cat) of 1000 M, which is extremely efficient for a bimolecular reaction catalyzed by an antibody. The hapten used to elicit this antibody is a derivative of endo hexachloronor-bomene. which is a shape mimic of the transition state. Because it has less structural similarity to the aromatic product, product inhibition in the lE9-catalyzed reaction is avoided. 

Although this alkylation/metathesis approach is certainly quite flexible and reasonably short, a one-step route to RTILs would be ideal. (Scheme 3) Several different attempts to achieve this goal have been reported, including one-pot reactions (in which alkylation and metathesis are combined),i alkylations using species other than alkyl halides (such as alkyl sulfonates, eliminating the need for anion metathesis), Michael reactions with reactive Michael acceptors, and simple protonation using strong acids. ... 

When the reaction conditions employed in all the steps are the same as those for the Peterson reaction, multi-step processes involving the Peterson reaction can be integrated in a one-pot process. Successive treatment of aDyl sulfones 234 with BuLi, MejSiCl, BuLi, aldehydes, and lithium hexamethyldisilazide(LiHMDS) gives the enynes in good to moderate overall yields for the four-step reactions (silylation, carbon-carbon bond formation, Peterson elimination, and sulfone elimination) (Scheme 2.144). The Peterson and sulfone eliminations can be successfully combined since both processes are carried out under basic conditions [152,153]. 

For chemical processes, some examples are the elimination of aromatics by sulfonation, the elimination of olefins by bromine addition on the double bond (bromine number), the elimination of conjugated diolefins as in the case of the maleic anhydride value (MAV), and the extraction of bases or acids by contact with aqueous acidic or basic solutions. 

The Julia-Lythgoc olefination operates by addition of alkyl sulfone anions to carbonyl compounds and subsequent reductive deoxysulfonation (P. Kocienski, 1985). In comparison with the Wittig reaction, it has several advantages sulfones are often more readily available than phosphorus ylides, and it was often successful when the Wittig olefination failed. The elimination step yields exclusively or predominantly the more stable trans olefin stereoisomer. 

Allylic sulfones undergo Pd-catalyzed elimination. The synthesis of an a,ft-unsaturated ketone by the elimination of the allylic sulfone group in 503 is an examplc[339]. 

Sulfonate esters are subject to the same limitations as alkyl halides Competition from elimination needs to be considered when planning a functional group transforma tion that requires an anionic nucleophile because tosylates undergo elimination reactions just as alkyl halides do... 

In some cases, a mixture of natural petroleum feedstock is preblended with synthetic alkylated aromatics, such as detergent aromatic alkylate bottoms or with first-intent synthetic mono- or dialkylated aromatics, selected to provide a suitable molecular weight for cosulfonation and subsequent processing. The use of blended feedstocks may eliminate the need for conducting an oil extraction—concentrating step, particularly for a typical 40% Ca or Mg petroleum sulfonated product. 

The simplest monomer, ethylenesulfonic acid, is made by elimination from sodium hydroxyethyl sulfonate and polyphosphoric acid. Ethylenesulfonic acid is readily polymerized alone or can be incorporated as a copolymer using such monomers as acrylamide, aHyl acrylamide, sodium acrylate, acrylonitrile, methylacrylic acid, and vinyl acetate (222). Styrene and isobutene fail to copolymerize with ethylene sulfonic acid. 

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