Reaction with sulfone anions

As mentioned above in connection with the acetic acid synthesis, iridium complexes catalyze the water-gas shift reaction (equation 70). From IrCl3-3H20 and sulfonated derivatives of bipy and phen, water-soluble catalysts were obtained.444 Using dioxane as solvent, complexes of the type [Ir(cod)L2]+ (L= PMePh2, PPh3), [Ir(cod)L ]+ (L = diphos, phen, 4,7-Me2-phen, 4,7-Ph2-phen, 3,4,7,8-Me4-phen) and [Ir(cod)X] (X = 4,7-diphenylphenanthroline disulfonate) also catalyzed the reaction, with the anionic species being most active.470 The mechanism was thought... 

The resistance of the furoxan ring to chemical attack allows derivatives to be prepared via the reactions of the substituents (Section 4.22.3.4). Carboxylic acids are available by permanganate oxidation of methyl derivatives or by hydrolysis of the corresponding esters reaction with ammonia affords carboxamides. Acylfuroxans provide a source of hydroxyalkyl compounds by reduction, and oximes, for example, via nucleophilic addition. Acylation and oxidation of aminofuroxans allows the amide and nitro derivatives to be prepared. Nucleophilic displacements of nitro substituents can take place, but can be somewhat hazardous on account of the explosive nature of these compounds. Alkoxy derivatives are formed with sodium alkoxide, while reaction with thiolate anions yields sulfides, from which sulfones can be synthesized by peracid oxidation. Nitrofuroxans have also been reduced to... 

The reaction of a,/ -unsaturated sulfones with chloroform, carried out under base/phase-trans-fer catalyst conditions, depends on the type of substituent on the sulfonyl group. Thus, phenyl vinyl sulfone underwent the Michael reaction with trichloromethyl anion to give 1, while ethyl vinyl sulfone underwent addition of dichlorocarbene to give cyclopropane 2. °... 

The vast literature on applications of PTC in substitution reactions is mainly restricted to nucleophilic substitution reactions with an anionic reagent. However, recently the use of PTC in electrophilic reactions, like diazotization andazocou-pling C-and N-nitrosation, C-alkylation, acid hydrolysis of esters, chloromethylation, nitrite-initiated nitrations, and so on have been reported(Velichko et al., 1992 Kachurin et al., 1995). Alkylbenzene sulfonates and lipophilic sodium tetrakis[3,5-bis(trifluoromethyl)phenylboranate are typical electrophilic PT catalysts. Lipophilic dipolar molecules of the betaine type and zwitterionic compounds also function well as PT agents for both nucleophilic as well as electrophilic reactions. 

Electrophilic Silylation Reagent. l,2-Bis(chlorodimethyl-silyl)ethane is not only an effective amine silylating reagent, but can also be employed in reactions with other anions. For example, when treated with the silver sulfonate salt as in eq 11, the nonafluorobutanesulfonic acid silyl ester (27), an extremely powerful silylating reagent, results.Carbanions are also effectively trapped by (1) A series of rigid butadiene Diels-Alder precursors such as (28) have been prepared in this fashion as outlined in eq 12.12... 

The higjily water-soluble dienophiles 2.4f and2.4g have been synthesised as outlined in Scheme 2.5. Both compounds were prepared from p-(bromomethyl)benzaldehyde (2.8) which was synthesised by reducing p-(bromomethyl)benzonitrile (2.7) with diisobutyl aluminium hydride following a literature procedure2.4f was obtained in two steps by conversion of 2.8 to the corresponding sodium sulfonate (2.9), followed by an aldol reaction with 2-acetylpyridine. In the preparation of 2.4g the sequence of steps had to be reversed Here, the aldol condensation of 2.8 with 2-acetylpyridine was followed by nucleophilic substitution of the bromide of 2.10 by trimethylamine. Attempts to prepare 2.4f from 2.10 by treatment with sodium sulfite failed, due to decomposition of 2.10 under the conditions required for the substitution by sulfite 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. 

A.lkyl Sulfosuccinate Half Asters. These detergents are prepared by reaction of maleic anhydride and a primary fatty alcohol, followed by sulfonation with sodium bisulfite. A typical member of this group is disodium lauryl sulfosucciaate [26838-05-1]. Although not known as effective foamers, these surfactants can boost foams and act as stabilizers when used ia combination with other anionic surfactants. In combination with alkyl sulfates, they are said to reduce the irritation effects of the latter (6). 

Solvent for Displacement Reactions. As the most polar of the common aprotic solvents, DMSO is a favored solvent for displacement reactions because of its high dielectric constant and because anions are less solvated in it (87). Rates for these reactions are sometimes a thousand times faster in DMSO than in alcohols. Suitable nucleophiles include acetyUde ion, alkoxide ion, hydroxide ion, azide ion, carbanions, carboxylate ions, cyanide ion, hahde ions, mercaptide ions, phenoxide ions, nitrite ions, and thiocyanate ions (31). Rates of displacement by amides or amines are also greater in DMSO than in alcohol or aqueous solutions. Dimethyl sulfoxide is used as the reaction solvent in the manufacture of high performance, polyaryl ether polymers by reaction of bis(4,4 -chlorophenyl) sulfone with the disodium salts of dihydroxyphenols, eg, bisphenol A or 4,4 -sulfonylbisphenol (88). These and related reactions are made more economical by efficient recycling of DMSO (89). Nucleophilic displacement of activated aromatic nitro groups with aryloxy anion in DMSO is a versatile and useful reaction for the synthesis of aromatic ethers and polyethers (90). 

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. 

It is often advantageous to proceed to a desired product through two nucleophilic displacements rather than directly when one can exploit a difference in the reactivity of two leaving groups. An example is the conversion of 4-chloro-2,6-dimethoxypyrimidine (109) (not satisfactorily reactive with sulfanilamide anion) by means of trimethylamine into the more reactive trimethylammonio derivative 110. Conversion of chloro-quinohnes and -pyrimi-dines into nitriles is best accomplished by conversion (with sulfite) into the sulfonic acids before reaction with cyanide. 

At the same time, the reaction of 1,2,4-triazine 4-oxides 55 with the anion of chloromethyl phenyl sulfone affords 5-(l-chloro-l-phenylmethyl)-l,2,4-triazines 66. In this case, autoaromatization of the a -adducts proceeds by the deoxygenative... 

Thiols, the sulfur analogs of alcohols, are usually prepared by Sjv 2 reaction of an alkyl halide with thiourea. Mild oxidation of a thiol yields a disulfide, and mild reduction of a disulfide gives back the thiol. Sulfides, the sulfur analogs of ethers, are prepared by an Sk2 reaction between a thiolate anion and a primary or secondary alkyl halide. Sulfides are much more nucleophilic than ethers and can be oxidized to sulfoxides and to sulfones. Sulfides can also be alkylated by reaction with a primary alkyl halide to yield sulfonium ions. 

Addition products are exclusively obtained from the addition of a-lithiatcd alkyl sulfones to a,/i-unsaturaled ketones5-6, in contrast, 1,4-adducts were obtained as a mixture of diastereomers from the reaction of these anions with a./l-unsaturated esters. The extent of the diastereoselection, however, was not reported6. 

In addition to protons, other electrofugic leaving groups such as SO3 (i. e., anions of sulfonic acids), Cl, Br, I, C02, and others can also be displaced in azo coupling reactions with aromatic substrates. The mechanism of such substitutions is in principle the same as that of dehydrogenation (see Fischer and Zollinger, 1972). 

Potassium or lithium derivatives of ethyl acetate, dimethyl acetamide, acetonitrile, acetophenone, pinacolone and (trimethylsilyl)acetylene are known to undergo conjugate addition to 3-(t-butyldimethylsiloxy)-1 -cyclohexenyl t-butyl sulfone 328. The resulting a-sulfonyl carbanions 329 can be trapped stereospecifically by electrophiles such as water and methyl iodide417. When the nucleophile was an sp3-hybridized primary anion (Nu = CH2Y), the resulting product was mainly 330, while in the reaction with (trimethylsilyl)acetylide anion the main product was 331. 

This review is concerned with the formation of cation radicals and anion radicals from sulfoxides and sulfones. First the clear-cut evidence for this formation is summarized (ESR spectroscopy, pulse radiolysis in particular) followed by a discussion of the mechanisms of reactions with chemical oxidants and reductants in which such intermediates are proposed. In this section, the reactions of a-sulfonyl and oc-sulfinyl carbanions in which the electron transfer process has been proposed are also dealt with. The last section describes photochemical reactions involving anion and cation radicals of sulfoxides and sulfones. The electrochemistry of this class of compounds is covered in the chapter written by Simonet1 and is not discussed here some electrochemical data will however be used during the discussion of mechanisms (some reduction potential values are given in Table 1). 

Polyphosphazenes sulfonates XIX with the anion covalently attached to the polymer are a new class of cation conductors that have been synthesized by Shriver [625]. They were obtained by reaction of Na0C2H4S03Na with an excess of polydichlorophosphazene in the presence of 15-crown-5, followed by the reaction of the partially substituted product with the sodium salt of poly(ethylene glycol methyl ether). The conductivity at 80 °C of the polymer with x=1.8, m=7.22 is 1.7x10 S cm This low conductivity can be attributed to an extensive ion pair formation between the sodium and sulfonate ions. 

In view of this behavior, the next step involved a search for an anionic sohd that was more similar to triflate. Several organic polymers with sulfonic groups were tried as supports [52]. Dowex and Deloxan were used as supports for the enf-6a-Cu(II) complex. The solid catalysts were used in the same cyclopropanation reaction (Scheme 7) and some relevant results are gathered in... 

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