Sulfone anion

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. 

All lation. In alkylation, the dialkyl sulfates react much faster than do the alkyl haHdes, because the monoalkyl sulfate anion (ROSO ) is more effective as a leaving group than a haHde ion. The high rate is most apparent with small primary alkyl groups, eg, methyl and ethyl. Some leaving groups, such as the fluorinated sulfonate anion, eg, the triflate anion, CF SO, react even faster in ester form (4). Against phenoxide anion, the reaction rate is methyl triflate [333-27-7] dimethyl sulfate methyl toluenesulfonate [23373-38-8] (5). Dialkyl sulfates, as compared to alkyl chlorides, lack chloride ions in their products chloride corrodes and requires the use of a gas instead of a Hquid. The lower sulfates are much less expensive than lower bromides or iodides, and they also alkylate quickly. 

Addition of 2-butenyl sulfone anions to 2-cyclopentenone and 2-cyclohexenone at low temperatures ( — 85 °C) gives mixtures of y-1, 4- and a-1,2-addition products. When these reactions are warmed to 1 2CC, then y-l,4-addition products predominate7,8. The lithium salts of the a-1,2-adducts rearrange to 1,4-adducts at 0°C. 

Salts of diazonium ions with certain arenesulfonate ions also have a relatively high stability in the solid state. They are also used for inhibiting the decomposition of diazonium ions in solution. The most recent experimental data (Roller and Zollinger, 1970 Kampar et al., 1977) point to the formation of molecular complexes of the diazonium ions with the arenesulfonates rather than to diazosulfonates (ArN2 —0S02Ar ) as previously thought. For a diazonium ion in acetic acid/water (4 1) solutions of naphthalene derivatives, the complex equilibrium constants are found to increase in the order naphthalene < 1-methylnaphthalene < naphthalene-1-sulfonic acid < 1-naphthylmethanesulfonic acid. The sequence reflects the combined effects of the electron donor properties of these compounds and the Coulomb attraction between the diazonium cation and the sulfonate anions (where present). Arenediazonium salt solutions are also stabilized by crown ethers (see Sec. 11.2). 

Aldol addition and related reactions of enolates and enolate equivalents are the subject of the first part of Chapter 2. These reactions provide powerful methods for controlling the stereochemistry in reactions that form hydroxyl- and methyl-substituted structures, such as those found in many antibiotics. We will see how the choice of the nucleophile, the other reagents (such as Lewis acids), and adjustment of reaction conditions can be used to control stereochemistry. We discuss the role of open, cyclic, and chelated transition structures in determining stereochemistry, and will also see how chiral auxiliaries and chiral catalysts can control the enantiose-lectivity of these reactions. Intramolecular aldol reactions, including the Robinson annulation are discussed. Other reactions included in Chapter 2 include Mannich, carbon acylation, and olefination reactions. The reactivity of other carbon nucleophiles including phosphonium ylides, phosphonate carbanions, sulfone anions, sulfonium ylides, and sulfoxonium ylides are also considered. 

Among the olefination reactions, those of phosphonium ylides, phosphonate anions, silylmethyl anions, and sulfone anions are discussed. This chapter also includes a section on conjugate addition of carbon nucleophiles to a, (J-unsaturated carbonyl compounds. The reactions in this chapter are among the most important and general of the carbon-carbon bond-forming reactions. 

Fig. 12 An example of guanidinium-sulfonate superstructures. The fundamental interaction responsible for both robustness and flexibility is the charge-assisted (+)N-H---0( ) hydrogen bonding between the guanidinium cations and the sulfonate anions, which can be varied in shape and length [44]...

Scheme 52 Sulfone anion radical in the reductive cleavage of arylsulfones.

Lastly, the anodic oxidation of sulfone anions could be achieved. Examples of the dimer formation are available in a recent paper [242]. The activity of a-sulfonyl anions at a positively polarized electrode was pointed out. The coupling of a,a-bissulfonyl anions by anodic oxidation was also achieved. These coupling reactions... 

The frequency of the symmetric stretch does not vary with degree of neutralization for hydrated membranes, which was attributed to the shielding of sulfonate anions from the electrostatic field of the Na+ ions. 

As described, other nucleophilic reactions in the anthraquinone series also involve the production of anion-radicals. These reactions are as follows Hydroxylation of 9,10-anthraquinone-2-sulfonic acid (Fomin and Gurdzhiyan 1978) hydroxylation, alkoxylation, and cyanation in the homoaromatic ring of 9,10-anthraquinone condensed with 2,1,5-oxadiazole ring at positions 1 and 2 (Gorelik and Puchkova 1969). These studies suggest that one-electron reduction of quinone proceeds in parallel to the main nucleophilic reaction. The concentration of anthraquinone-2-sulfonate anion-radicals, for example, becomes independent of the duration time of the reaction with an alkali hydroxide, and the total yield of the anion-radicals does not exceed 10%. Inhibitors (oxygen, potassium ferricyanide) prevent formation of anion-radicals, and the yield of 2-hydroxyanthraquinone even increases somewhat. In this case, the anion-radical pathway is not the main one. The same conclusion is made in the case of oxadiazoloanthraquinone. 

As carriers for ion exchangers they find application in HPLC. Cation exchangers are prepared by sulfonation, anion exchangers are prepared by nitration. Reduction to amines and alkylation, are achieved through quarternation and chloromethylation, respectively. 

In the last family, the sulfonate anion is attached to a neutral alkyl spacer unit [-(CH2) -, where n = 2 to 6] that links to the CD structure by a metabolically stable ether linkage. This group of compounds differs from the first two families in that the anionic charge is spaced away from the carbohydrate backbone by the alkyl group. 

The loss of stereospecificity in the addition of bis(sulfone) anions to cyclohexenyl allylic acetates was attributed to a scrambling of the stereochemistry of the starting acetate. The ability of Pd° catalyst to effect this epimerization was confirmed in the absence of added nucleophile. This epimerization was attributed to the ability of the acetate to return to add to the ir-allyl complex via attack at the metal center (equation 177).167 This suggestion was confirmed by treatment of a preformed allylpalladium acetate dimer with CO, which resulted in cis migration of the acetate from Pd to the allyl ligand (equation 178).164... 

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