Sulfonic acid, polymer-supported

TsOH, THF, CH2CI2,5 min. This method was developed for solid-phase peptide synthesis as a safe large-scale alternative to the use of TFA, which is expensive, corrosive, and a waste problem on a large scale. The reaction is accelerated with microwave irradiation. Polymer-supported sulfonic acids such as Am-berlyst 15 effectively cleave the BOC group and leave it loaded on the resin. Washing with NH4OH releases the free amine from the resin in pure form. ... 

SSA is a better proton source than polymer-supported sulfonic acids such as polystyrene sulfonic acid and Nafion-H. Many reactions using SSA have been reported, such as multicomponent reactions [68-76], carbon-oxygen [77-86], carbon-nitrogen [87-93] and carbon-sulfur [94, 95] bond formation or cleavage. 

The objective of the present work is to discover whether the same sort of acidity/activity enhancements seen for polymer-supported sulfonic acids can be obtained on more rigid inorganic supports. Acid strengths of the two types of catalyst have been measured in both the absence of solvent as molar enthalpies of ammonia adsorption, and in the presence of water through molar enthalpies of neutralisation with aqueous NaOH solution. Catalytic activities have been measured in water for the hydrolysis of ethylethanoate. 

Scheme 18.5 Steps in the synthesis of trilobolide requiring orthogonal protection and deprotection using polymer-supported sulfonic acid.

Finally, compound 38 had to be epimerized to epibatidine, and this was best done using microwave heating in the presence of potassium f-butoxide in f-butanol. This was one of the early examples of focused microwave heating. The natural product was then isolated by catch-and-release caught with a polymer-supported sulfonic acid followed by release using methanolic ammonia. 

General. Polymer-supported sulfonic acids are reliable catalysts for many acid-mediated reactions. Macroretlcular poly-styrene-based resins such as Amberlyst 15 are preferentially used in organic solvents, whereas Dowex resins work better in aqueous solutions. All resins are insoluble and can be separated from reactions by simple filtration. 

Another application of trifluoromethyl phenyl sulfone is in the preparation of benzenesulfonic acid (or metal benzenesulfonate) using oxygen nucleophiles. Trifluoromethyl phenyl sulfone is readily transformed into benzenesufonate salt upon treatment with an alkoxide or hydroxide (eq 6). This is particularly useful for the convenient transformation of a polymer-supported trifluoromethyl phenyl sulfone into polymer-supported sulfonic acid (or sufonate) ion-conducting materials. " ... 

Several coumarins starting from appropriate phenolic compounds have been synthesized in a microwave-assisted reaction using trifluoroacetic acid, which acts as an acidic reagent and a reaction medium. Alternatively, polymer-supported sulfonic acid Amberlyst-15 could also be utilized to assist the formation of coumarins. The usage of a particularly built microwave synthesizer with liquid handling tools rendered the automated synthesis of a coumarin library achievable (07CHE151). 

Polymer supported persulfonic acids can be prepared by treating polymer-bound sulfonic acids with H2O2 or K2S20g. The resulting resin was found to display an activity of 2.5 mole equivalents per gram of wet resin. This persulfonated resin was successively applied for the oxidation of carboxylic acids, ketones, olefins and for the cleavage of disulfide linkage and of A-formylamino acids. 

A variety of organic peroxy acids such as perbenzoic acid, MCPBA. monoperoxyphthalic acid, peracetic acid and trifiuoroperacetic acid are much stronger oxidants dian H2O2, and oxidize sulfides to sulfoxides under very mild conditions. Usually 1 equiv. of peroxy acid to sulfide is employed, otherwise overoxidation easily occurs to give sulfones. Among these, MCPBA has die advantage of being convenient to use and Ae oxidation is normally carried out at 0 C or lower temperatures, in di-chloromethane. The preparations of the base-sensitive sulfoxide (15), a new dienophile alkynyl sulfoxide (16), " and thiiraneradialene S-oxide (17) are typical examples. Selective oxidation of the sulfur atom of penicillins by polymer-supported peroxy acids in DMF or acetone is also known (equation 17). ... 

The liquid composition of Nafion , approximately 5 wt% solution, was used to coat the calcined shot coke (10-20 mesh, 0.42m /gram). Loadings were varied up to 3 wt%. The oligomerization of isobutylene in toluene at 110°C was used to measure the activity of the sulfonic acid catalysts. Table 4 compares the activity of several supported and non-supported sulfonic acid polymers. The... 

It is instructive to compare these new supported sulfonic acids with the well established polystyrene-supported sulfonic acids which have been used as acid catalysts in reactions such as MTBE synthesis for many years. These sulfonated polymers are generally thought to be limited in application because of their relatively low acid strength and poor stability at reaction temperatures above 150 However, we and others have... 

The results show clearly that, in the presence of water, the acid catalytic activity of supported sulfonic acid groups is essentially the same on polymer and silica supports, except where the level of polymer sulfonation is high, when the sulfonic acid exhibits significantly enhanced activity. The trend in molar enthalpies of neutralisation with aqueous NaOH is similar. On silica supports, and polymer supports with low sulfonic acid concentrations, these enthalpies are very similar to those of strong mineral acid solutions. In contrast, resins with high levels of sulfonation show significantly higher molar enthalpies of neutralisation. 

Nafion is a perfluorinated polymer with sulfonic acid groups grafted to side chains, yielding acidity similar to that of sulfuric acid [5]. Nafion has not been extensively studied as a catalyst for isoparaffin alkylation, although it has shown good activity for a number of acid catalyzed reactions [6-9]. Nafion is available in both unsupported and supported forms. In the supported form, the polymer is impregnated on high surface area silica supports, which has been shown to improve accessibility to acid sites [10,11]. 

The physical nature of the polymer that supports the sulfonic acid functionality appears to play a minor role in these reactions. Suzuki has reported the use of a silica-supported sulfonic acid as an efficient acid catalyst for the vapor-phase nitration of benzene with gaseous NO2 to give nitrobenzene (20) (eq 21). This nitration process is particularly efficient as it gives nitrobenzene in 93% yield. 

Polymer supported reagents, catalysts, protecting groups, and mediators can be used in place of the corresponding small molecule materials (Sherrington, 1991 Sundell and Nasman, 1993). The reactive species is tightly bound to a macromolecular support which immobilizes it. This generally makes toxic, noxious, or corrosive materials much safer. The use of polystyrene sulfonic acid catalyst for the manufacture of methyl r-butyl... 

However, the mechanism of action of filtration control additives is not yet completely understood. Examples are bentonite, latex, various organic polymers, and copolymers. Many additives for fluid loss are water-soluble polymers. Vinyl sulfonate fluid loss additives based on the 2-acrylamido-2-methyl-propane sulfonic acid (AMPS) monomer are in common use in field cementing operations [363]. The copolymerization of AMPS with conjugate monomers yields a fluid loss agent whose properties include minimal retardation, salt tolerance, high efficiency, thermal stability, and excellent solids support. 

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