Sulfone anion addition

In a study by Wicha directed to the synthesis of prostaglandins from the Corey lactone, the use of BFs-EtaO to catalyze the addition of the lithium sulfone anion (470) to aldehydes was demonstrated (equation 109). The use of Lewis acid catalysis results in significantly improved yields for the addition component of the Julia coupling. In this example, the addition of either the lithium or the magnesium sulfone anion proceeded in low yield. With the addition of BF3-Et20, the p-hydroxy sulfone can either be isolated, or directly converted to an alkene in one pot. This sequence was originally developed to deal with the specific problem of a-hydroxy aldehydes, and the difficulty of sulfone anion addition to these adducts. Other problems with addition of the sulfone adduct may be amenable to this solution as well. 

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. 

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. 

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. 

Spontaneous polymerization of 4-vinyl pyridine in the presence of polyacids was one of the earliest cases of template polymerization studied. Vinyl pyridine polymerizes without an additional initiator in the presence of both low molecular weight acids and polyacids such as poly(acrylic acid), poly(methacrylic acid), polyCvinyl phosphonic acid), or poly(styrene sulfonic acid). The polyacids, in comparison with low molecular weight acids, support much higher initial rates of polymerization and lead to different kinetic equations. The authors suggested that the reaction was initiated by zwitterions. The chain reaction mechanism includes anion addition to activated double bonds of quaternary salt molecules of 4-vinylpyridine, then propagation in the activated center, and termination of the growing center by protonization. The proposed structure of the product, obtained in the case of poly(acrylic acid), used as a template is ... 

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... 

The first step in this multistage reaction is the nucleophilic addition of sulfone anion 28 to aldehyde 8 (Scheme 14.6). This produces a p-alkoxysulfone intermediate 29 which is trapped with acetic anhydride. The resulting P acetoxysulfone mixture 22 is then subjected to a reductive elimination with Na/Hg amalgam to obtain alkene 23. The tendency of Julia-Lythgoe-Kocienski olefinations to provide ( )-1,2-disubstituted alkenes can be rationalised if one assumes that an a-acyloxy anion is formed in the reduction step, and that this anion is sufficiently long-lived to allow the lowest energy conformation to be adopted. Clearly, this will... 

Polyester fibers can be given an additional mechanism for dyeing if an ionic comonomer is added during polymerization. A common additive is an alkali metal salt of dimethyl-5-sulfo-isophthalate, which gives sulfonic (anionic) groups as part of the polymer structure. These groups allow the fiber to absorb... 

Since the ammoniiun cations are placed in the middle and the sulfonate anions at the end of the side chain of 23b, the complex can be solubilized due to free anionic groups of 23b (Scheme 19a). In contrast, PDMAPAA-Q and ionenes bind to 23b via the sulfonate groups, which are located at the end of side chain (Scheme 19b and c). The ammonium cations of PDMAPS are thus strongly shielded as hydrophilic solubihzing groups because they are surrounded by two hydrophobic polymer main chains in the complex. Table 3 summarizes the yields and UCSTs of the IPCs resulting from the addition of anionic (PAA, PMAA, NaPSS), cationic (polyDADMAC, PDMAPAA-Q), and nonionic (polyacrylamide, PAAm) polymers to 23b. 

Lewis Acid Catalyzed Additions of Sulfone Anions to Carbonyls... 

The Julia coupling has also been successfully utilized for the synthesis of more complex alkenes. There are limitations to the application of the method to tri- and tetra-substituted alkenes, since the addition of the sulfone anion to a highly substituted ketone forms a -alkoxy sulfone that is difficult to trap and isolate. There is a tendency for highly substituted p-alkoxy sulfones to revert back to the ketone sulfone. There have been several recent examples of the synthesis of trisubstituted ( )-alkenes worthy of note. 

As discussed in the sections above, the sulfonylmethane anion reacts with ketones and aldehydes che-moselectively in the presence of an ester or amide. It is possible to obtain the keto sulfone on addition to an ester (448) when the reaction is carried out without competing carbonyl groups (equation lOS). The... 

The Julia olefination reaction is highly regioselective and ( )-stereoselective, providing a valuable alternative to the Schlosser reaction for making rrans -disubstituted olefins. The reaction involves condensation of a metalated alkyl phenyl sulfone with an aldehyde to yield a P-hydroxysulfone, which is then subjected to a reductive elimination to produce the alkene. There are limitations to the preparation of tri- and tetra-substituted alkenes via the sulfone route because the P-alkoxy sulfones derived from addition of the sulfone anion to ketones may be difficult to trap and isolate or they may revert back to their ketone and sulfone precursors. 

The Pt-catalyzed hydrosilylation of trimethyl silane and alkenols or alkenyl-polyethers lead to nonionic silane surfactants, whereas the addition of allylglycidyl ether to trimethylsilane results in a precursor for ionic derivatives. The epoxy group is highly reactive towards nucleophilic agents and can be easily transformed into quaternary ammonium, betaine, or sulfonate complexes. Additionally, cation-anion complexes can be formed by the transformation of two equivalents of epoxy silane with one equivalent of trialkyl ammonium hydrogen sulfite. The reaction of hydroxyalkyltrimethylsilane... 

---