Sulfonyl halides, properties

Normally, reactive derivatives of sulfonic acids serve to transfer electrophilic sulfonyl groups259. The most frequently applied compounds of this type are sulfonyl halides, though they show an ambiguous reaction behavior (cf. Section III.B). This ambiguity is additionally enhanced by the structure of sulfonyl halides and by the reaction conditions in the course of electrophilic sulfonyl transfers. On the one hand, sulfonyl halides can displace halides by an addition-elimination mechanism on the other hand, as a consequence of the possibility of the formation of a carbanion a to the sulfonyl halide function, sulfenes can arise after halide elimination and show electrophilic as well as dipolarophilic properties. 

A reaction which is related to hydroxy-de-diazoniations is the formation of aryl trifluoromethylsulfonic esters (aryl triflates, ArOSC CFs) which became widely used reagents because of their leaving-group properties. The classical method of synthesis by esterification of phenols with trifluoromethane-sulfonic anhydride or -sulfonyl halide is, however, not applicable for the preparation of aryl triflates bearing a (free)... 

Sulfhydryl group, 117 in /3-amylases, 334 in phosphorylases, 347 Sulfones, of 5-thioaldopyranoses, 212 Sulfonic anhydrides, sulfonylation of carbohydrates by, 238 Sulfonic esters of carbohydrates, 233 — 280 physical properties and chemical stability of, 253,257 Sulfonylation, of carbohydrates selective, 240, 244 by sulfonyl halides, 236... 

Sulfonyl halides, particularly arenesulfonyl halides, can afford radical species much faster than carbon halides by the assistance of a metal complex and efficiently add to olefins with little dimerization of sulfonyl radicals in comparison to carbon-centered radicals. Another feature of the compounds is that there is little effect of the substituents on the rate of addition to an olefin. These properties make sulfonyl halides an efficient and universal series of initiators for the metal-catalyzed living radical polymerizations of various monomers including methacrylates, acrylates, and styrenes (Figure g). 52.175-177... 

As a class, sulfonic acids (RSO3H) are the strongest uncharged organic acids. Their acidities are similar to those for the strong mineral acids. Selected physical properties for these materials are given in Tables 3, 4A and 4B. Selected physical properties for the alkane-sulfonyl halides and anhydrides in common commercial and laboratory use are provided in Table 5. 

Table 5 Physical properties of selected sulfonyl halides and anhydrides ...

The difference in the atomic radii, the electronegativities of the halogen atoms and the S—X bond strengths resulted in a gradual change in the properties of the four sulfonyl halides which are manifested in the following paragraphs. 

Rh(TTP) reacts with alkyl halides, acyl halides, aroyl halides, and sulfonyl halides, but it shows no evidence of reaction with molecular hydrogen. These observations further emphasize the fact that Rh(TTP) is essentially a nucleophile and it therefore reacts with those reagents RX that can oxidatively add by nucleophilic attack (34). Rh(TTP) does not react with H2, and H2 seems always to add to (P complexes via a concerted mechanism (35). It appears that Rh(TTP) has very little diradical character, i.e. it is not a good analog of a carbene (35). It is possible that this unreactivity may be associated with the stereochemistry of chelation by the macrocyclic ligand. Earlier studies on the oxidative addition reactions of Rh(I) complex with a tetraaza macrocycle revealed that the Rh(I) had strong nucleophilic properties but the activation of molecular H2 was not reported (36, 37). This possibility is supported by reports that dialkyl sulfide complexes of rhodium chloride catalyze the hydrogenation of olefins (38). 

Sulfonate esters are exceedingly useful substrates in nucleophilic substitution reactions because of their high level of reactivity and because, unlike alkyl halides, they may be prepared from alcohols by reactions that do not directly involve the carbon atom at which subsequent substitution is to be effected. These properties are particularly important in cases where the stereochemical and structural integrity of the substrate must be maintained in converting an alcohol to a derivative capable of undergoing nucleophilic substitution. Sulfonate esters are commonly prepared by reaction of an alcohol with a sulfonyl halide in the presence of pyridine ... 

Numerous studies have been devoted to the addition of RSO2X to olefins. The propagation steps for these chain processes are shown in Scheme 13. The main factors controlling the reactivity of sulfonyl radicals are polar effects and the reversibility of the addition. Sulfonyl radicals exhibit an electrophilic character with respect to addition to olefins [98]. Evidence for the reversibility came early from the observation of the isomerization of cis- and rran -2-butenes during their copolymerization with sulfur dioxide and their Cu(I)-mediated reaction with benzenesulfonyl chloride [99]. Therefore, the chain transfer of alky] adduct radica]s has to compete effectively with -elimination of sulfonyl radicals (see Scheme 13). Selenosulfonates, sulfonyl halides, and sulfonyl cyanides are the most popular substrates that meet this property. 

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