Sulfones reaction with active

Albrecht and Wilhams [132,133] developed an interesting synthetic approach to macrocyclic proteasome inhibitors TMC-95A/B, involving reaction of BT sulfone 297 with activated ketone 298 (Scheme 96). The reaction was carried out using LHMDS, in DMF containing DMPU as the co-solvent, at 0 °C. The olefination product 299 was obtained in 79% yield, E/Z 5/1. 

Mercaptan groups in keratin fibers also undergo nucleophilic addition reactions with active olefins (olefins containing a strong electron-withdrawing group attached to the double bond). Schoberl [91] has shown that reduced wool fiber reacts with vinyl sulfones. 

In the same area, these authors have also investigated the efficiency of various chiral sterically congested phosphane-amide bifunctional organocatalysts with a binaphthyl scaffold in asymmetric aza-Morita-Baylis-Hillman reactions of A -sulfonated imines with activated olefins such as methyl and ethyl vinyl ketones." The corresponding aza-Morita-Baylis-Hillman adducts could be obtained in moderate to excellent yields (37-98%) and moderate to good... 

Shi, M., Chen, L-H., and U, C.-Q. (2005) Chiral phosphine Lewis bases catalyzed asymmetric aza-Baylis-Hillman reaction of N-sulfonated imines with activated olefins. J. Am. Chem. Soc., 127, 3790-3800. 

Fiber-Reactive Dyes. These dyes can enter iato chemical reaction with the fiber and form a covalent bond to become an iategral part of the fiber polymer. They therefore have exceptional wetfastness. Thein main use is on ceUulosic fibers where they are appHed neutral and then chemical reaction is initiated by the addition of alkaH. Reaction with the ceUulose can be by either nucleophilic substitution, using, for example, dyes containing activated halogen substituents, or by addition to the double bond in, for example, vinyl sulfone, —S02CH=CH2, groups. 

For aryl halides and sulfonates, even active ones, a unimolecular SnI mechanism (lUPAC Dn+An) is very rare it has only been observed for aryl triflates in which both ortho positions contain bulky groups (fe/T-butyl or SiRs). It is in reactions with diazonium salts that this mechanism is important ... 

As noted in the preceding section, one of the most general methods of synthesis of esters is by reaction of alcohols with an acyl chloride or other activated carboxylic acid derivative. Section 3.2.5 dealt with two other important methods, namely, reactions with diazoalkanes and reactions of carboxylate salts with alkyl halides or sulfonate esters. There is also the acid-catalyzed reaction of carboxylic acids with alcohols, which is called the Fischer esterification. 

With carboxylic acids there was no activation to carboxylic acid imidazolides observed. Reaction with p-toluenesulfonic acid in boiling tetrahydrofuran did not yield the />-toluenesulfonic acid imidazolide, but rather the double p-toluene sulfonate, from which A -sulfonyldiimidazole can be released again quantitatively with imidazole or aniline. Only from the melt of water-free p-toluenesulfonic acid and AyV -sulfonyldiimidazole at 90 °C p-toluenesulfonic imidazolide (m.p. 75.5-77 °C 87% yield) could be obtained1201 (see also Section 10.1.1). 

Tibric acid (10), interestingly, has the m-carboxysulfonamido functionality but its activity is expressed, instead, as suppression of serum triglyceride levels. In its reported preparation, chloro-sulfonic acid treatment converts 2-chlorobenzoic acid to chlorosulfonate 9, which readily forms the hypolipidemic agent tibric acid (10) on reaction with... 

The 2-pyridyl sulfones have been activated with Sm(OTf)3 in toluene at 70 °C. The reaction also proceeds in refluxing methylene chloride, albeit with slightly diminished yields (Scheme 4.56) [308]. The mechanism has not been studied in either case, but activation has been suggested to involve the complexation of the metal ion with the pyridyl nitrogen and one of the sulfur oxygens, followed by the cleavage of the Cl—S bond leading to an oxacarbenium ion, for the pyridyl sulfones. 

Based on nucleophilic addition, racemic allenyl sulfones were partially resolved by reaction with a deficiency of optically active primary or secondary amines [243]. The reversible nucleophilic addition of tertiary amines or phosphanes to acceptor-substituted allenes can lead to the inversion of the configuration of chiral allenes. For example, an optically active diester 177 with achiral groups R can undergo a racemization (Scheme 7.29). A 4 5 mixture of (M)- and (P)-177 with R = (-)-l-menthyl, obtained through synthesis of the allene from dimenthyl 1,3-acetonedicar-boxylate (cf. Scheme 7.18) [159], furnishes (M)-177 in high diastereomeric purity in 90% yield after repeated crystallization from pentane in the presence of catalytic amounts of triethylamine [158], Another example of a highly elegant epimerization of an optically active allene based on reversible nucleophilic addition was published by Marshall and Liao, who were successful in the transformation 179 — 180 [35], Recently, Lu et al. published a very informative review on the reactions of electron-deficient allenes under phosphane catalysis [244]. 

Since in principle the reactions of enantiomeric sulfoxides with a chiral reagent are expected to proceed at unequal rates, a possibility exists for obtaining chiral sulfoxides, especially when the reacting racemic sulfoxide is used in excess in relation to the chiral reagent. A typical example of such a kinetic resolution of a racemic sulfoxide is its reaction with a deficiency of chiral peracid, affording a mixture of optically active sulfoxide and achiral sulfone (62,63). However,... 

A highly efficient asymmetric induction was also observed in the addition of the lithium salt of (+)-(5)-34 to acetone (313). The addition product 297 (optical purity ca. 80%) was then oxidized to the corresponding sulfone 298, whose absolute configuration was established as R by means of chemical correlations. The formation of sulfone 298 with the absolute configuration R at carbon proves that, unlike methylation, the addition reaction takes place with retention of configuration. It is worthy of note that the optically active... 

This mechanism also applies to other CH2-active compounds such as derivatives of aroxyacetic acid and benzylic sulfones, whose methylation reactions with... 

In a study aimed at the identification of products of free radical reactions with polystyrene- and aromatic-based PEMs using model compounds, Hiibner and Roduner observed the addition of free radicals to the aromatic rings, preferentially in the ortho position to alkyl- and RO-substituents (in polystyrene- and aromatic-based PEMs, the para position is blocked by the presence of the sulfonic acid group). This study demonstrated the combined ortho-activation by these substituents and the meta-directing effect... 

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