Arylsulfonic groups

In the case where the arylsulfonate group is a benzene instead of a naphthalene the relaxation kinetics for guest complexation with a-CD measured by stopped-flow showed either one or two relaxation processes.185,190 When one relaxation process was observed the dependence of the observed rate constant on the concentration of CD was linear and the values for the association and dissociation rate constants were determined using Equation (3). When two relaxation processes were observed the observed rate constant for the fast process showed a linear dependence on the... 

Aryl sulfonates are the least reactive SM substrates since the C-O bond is less polarized and thus oxidative addition to palladium(0) or nickel(O) proceeds much slower. Furthermore, the steric demands of all common arylsulfonate groups are considerably higher than in any halide analogue. However, the SM reactions have been... 

Mocimycin has been chemically converted to aurodox by protection of the 4-hydroxy group at the pyridone moiety as the benzoylformate, followed by /V-methylation and hydrolytic removal of the protective group (1,55). Whereas aurodox esters are active growth promotors in animals, goldinamines that are A/-acylated by acids other than goldinonic acid, such as acetic, benzoic, or arylsulfonic acids, lack useful antimicrobial or growth-promoting activity (1). 

Fusion/Hydroxylation. The conversion of arylsulfonic acids to the corresponding hydroxy compound is normally effected by heating with caustic soda (caustic fusion). The primary examples are P-naphthol in the naphthalene series and resorcinol in the benzene series further examples are m- am in oph en o1 from metanilic acid and diethyl-y -arninophenol from /V,/V-diethy1metani1ic acid. In the naphthalene series the hydroxy group is much... 

It is evident from the foregoing sections that simple alkylvinyl halides do not react via an Sn 1 mechanism, if at all, even under extreme solvolytic conditions (146,149). More reactive leaving groups, such as arylsulfonates, were clearly needed to investigate the possible solvolytic behavior of simple alkylvinyl systems, but the preparation of vinyl sulfonates until recently was unknown. Peterson and Indelicato (154) were the first to report the preparation of vinyl arylsulfonates via reaction of the appropriate disulfonate with potassium t-butoxide in refluxing f-butanol. They prepared and investigated the solvolysis of 1-cyclohexenyl tosylate 169 and c/s-2-buten-2-yl tosylate 170 and the corresponding p-bromobenzenesulfonates (brosylates). Reaction... 

Another concern for polystyrene- and some aromatic-based PEMs is hydrolysis of fhe sulfonic acid group from aromatic rings as well as hydrolytic cleavage of polymer backbone under fuel cell conditions for aromafic polymers including polyimides, poly(arylene ethers), poly(ether ketones), and poly(ether sulfones). It is well known that the sulfonation of aromafic rings is a reversible process especially at low pH and at elevated temperature (Scheme 3.3). The reversibility of sulfonation, for example, is used in fhe preparafion of trinitrotoluene or picric acid. Por the simplest membrane of the class of arylsulfonic acids (i.e., benzenesulfonic acid), fhe reacfion occurs upon freatment with a stream of superheated steam at 180°C.i ... 

The effect of substrate structure on enantioselectivity has been explored for the catalytic intramolecular cyclopropanation reaction of a-diazo-/3-keto arylsulfones.56 It has especially been shown that substitution of the phenyl ring by a methyl at the ortho position of the sulfonyl group dramatically increased the ees, with values up to 93%. 

The fusion of alkali arylsulfonates with potassium cyanide forms aromatic nitriles by a replacement of the sulfo group. For the most part, the yields are low, although the reaction has been applied successfully in the preparation of naphthonitriles and cyanopyridines. Sometimes potassium ferrocyanide is substituted for the alkali cyanide with better results. Ten isomeric cyanonaphthalenesulfonates have been converted to the dinitriles by fusion with this reagent in yields ranging from 8% to 75%. Migration of the cyano group from the beta to the alpha position has been observed in the formation of these Compounds. ... 

Sulfonation of the aromatic nucleus (method 540) is a reversible reaction. The removal of a sulfonic acid group is important in the preparation of alkylated benzenes by the Jacobsen reaction (method 16). Ortho-disubstituted benzenes are sometimes prepared by using the sulfonic acid group to block the para position. The removal of the sulfonic acid group is usually effected by heating the arylsulfonic acid with aqueous sulfuric acid. 

Esters of arylsulfonic acids are generally reducible, and this has been employed for protection [40] of hydroxyl groups the cleavage of tosylates [150,154, 246-249] and nosy-lates (esters of 4-nitrobenzenesulfonic acid) [250] has especially been studied. 

Zeidan et al. [16] incorporated arylsulfonic acid and alkylthiol groups into mes-oporous silica by a cocondensation method, where 2-(4-chlorosulfonylphenyl)-ethyl-trimethoxysilane and 3-mercaptotrimethoxysilane were added to tetraethyl orthosilicate, forming a mesoporous silica (SBA-15) material via a sol-gel process (Fig. 23.4a). The resulting catalysts exhibited far greater activity and selectivity than materials containing only the acid. These randomly distributed catalysts achieved in the best case a per site yield (defined as moles of product per mole of sulfonic acid) of 82 and a 95% selectivity for bisphenol A, compared to a per site yield of 18 and 58% selectivity for bisphenol A when using homogeneous sulfonic acid alone. 

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