Polystyrene supported sulfonic acid

Pt-catalyzed hydration of various aliphatic and aromatic alkynes under phase transfer conditions in (CH2C1)2/H20 in the presence of Aliquat 336 led to either a Markovnikov product, mixtures of two ketones, or ketones with the carbonyl group positioned away from the bulky side.72 In the absence of the phase transfer reagent, Aliquat 336, hardly any reaction took place. Recently, a hydrophobic, low-loading and alkylated polystyrene-supported sulfonic acid (LL-ALPS-SO3H) has also been developed for the hydration of terminal alkynes in pure water, leading to ketones as the product.73 Under microwave irradiation, the hydration of terminal arylalkynes was reported to proceed in superheated water (200°C) without any catalysts.74... 

Another variation on this theme is the use of a scandium salt of a hydrophobic polystyrene-supported sulfonic acid (PS-S03H) as an effective heterogeneous Lewis acid catalyst in aqueous media [149]. 

Low-loading alkylated polystyrene-supported sulfonic acid, water, 40°C, 12-24 h, 76-94% yield. A tertiary TBDMS ether was not cleaved. A TBDMS can be cleaved in the presence of a TBDPS ether. TIPS, TBDPS, OTr, OMOM ethers, and an acetate can all be cleaved, but the authors do not indicate relative rates... 

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 most widely used catalysts for acid-catalyzed aldol condensations are the molecular sieve zeolites, for example, crystalline aluminosilicates of group I and II elements, in which the latter have been replaced by protons. The surface protons confer Br0nsted acidity. Among the acidic zeolites we can mention HZSM-5 (pentasil zeolite), HY (faujasite), or HM (mordenite). Recently, polystyrene-supported sulfonic acids such as those of the macroreticular strongly acidic cation-exchange resins (59) and acid-base functionalized mesoporous materials such as amine and sulfonic acid-containing SBA-15 (60) have been shown to promote the acid-catalyzed aldol condensation of aldehydes with ketones at low temperatures. 

Type of reaction C-N bond formation Reaction conditions Water, room temperature Synthetic strategy One-step condensation Catalyst Polystyrene supported sulfonic acid (PSSA)... 

It was found that dehydrative esterification in water was effectively catalyzed by hydrophobic polystyrene-supported sulfonic acids as recoverable and reusable catalysts. As shown in... 

Three-component Mannich-type reactions of aldehydes, amines, and silicon enolates also proceeded smoothly using PS-SO3H in water (Scheme 3.37). In general, ketene silyl acetals are known to be easily hydrolyzed in the presence of water however, such water-labile compounds could be successfully used in this reaction. Moreover, a remarkable effect of the loading levels of the polystyrene-supported sulfonic acid on yields was observed. It was suggested that the hydrophobic environment created by the catalyst might suppress hydrolysis of ketene silyl acetals. 

Furthermore, low-loading (e.g. 0.17 mmol/g) and alkylated polystyrene-supported sulfonic acid (LL-ALPSSO3H) such as 13 successfully calatyzed deprotection of tert-butyldimethylsilyl- (TBS) protected alcohols in water without using organic cosolvents (Scheme 3.38). 

A hydrophobic polystyrene-supported sulfonic acid showed high catalytic activity in water in the three-component Mannich reaction, with 1 mol% of catalyst being enough to catalyze the reaction (Scheme 8.16). ... 

Unsymmetrical 1,3-diketones give mixtures of structural isomers. The cyclocondensation is acid-catalyzed, for example, by a very efficient polystyrene-supported sulfonic acid [433], and proceeds via hydrazone or enehydrazine intermediates 15. 

Figure 4.1.28. (a) Polystyrene supported sulfonic acid, (b) Metal binding by two poly(amino acid) chains bound at one end to the pore surface of a membrane (Hestekin et al., 2001). Reprinted, with permission, from I EC Research, 40, 2668 (2001), Figure 1(a). Copyri t (2001) American Chemical Society, (c) Poly(amino acid) chains bound on the surface of a pore in a membrane. 

In recent years, the use of heterogeneous catalysis has received useful applications in various organic transformations due to several advantages over conventional homogeneous catalysis. Several solid acid catalysts [108] such as Amberlyst [109], solid-supported fluoroboric acid [110], polyaniline sulfate [111], polystyrene-supported sulfonic acids [112], sulfated zirconia [113], and silica [114] in conjunction with other greener techniques such as MW, US, environmentally benign solvents, solvent-free conditions, and so on have been screened, evaluated, and compared with respect to yields, reaction time, reaction temperature, ease of purification, reusability, toxicity, and other hazards for sustained applications. Many of these efforts have found applications in the medium ring-sized heterocycles such as oxepines, azepines, diazepines, oxazepines, thiazepines, and so on. 

Alternatively, sulfonamides can also be prepared by oxidation of sulfinamides with periodate (Entry 3, Table 8.8) or with MCPBA [125]. Polystyrene-bound sulfonyl chlorides, which can be prepared from polystyrene-bound sulfonic acids by treatment with PCI5, SOCI2 [126-129], CISO3H [130], or SO2CI2/PPI13 [131], react smoothly with amines to yield the corresponding sulfonamides (Entry 4, Table 8.8). Support-bound carbamates of primary aliphatic or aromatic amines can be N-sulfonylated in the presence of strong bases, and can therefore be used as backbone amide linkers for sulfonamides (Entries 5 and 6, Table 8.8). 

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. 

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... 

Only a few examples of solid-phase syntheses of phosphonic, phosphoric, and sulfonic acids have been reported (Figure 3.16). Benzyl esters of these strong acids can act as alkylating agents, and may therefore be too labile to serve as linkers for long synthetic sequences on solid phase. However, if cross-linked polystyrene is used as the support, the reactivity of, for example, benzyl sulfonates is strongly reduced, and even... 

Schiff base and related complexes of uranium and thorium are widely described in recent literature and covered in a review [463]. Those of U(VI) have a practical use as catalytic organic oxidants [460] or as part of a polystyrene-supported chelating resin [464,465]. Among other Schiff base precursors, salicylaldehyde [466] and triethylenetetramine [464], 3-formylsalicylic acid and o-hydroxybenzylamine [465], or salicylaldehyde and l-amino-2-naphthol-4-sulfonic acid [467] were used. In the example of Schiff base complexes, kinetics of formation of U(VI) complexes and their pK values were studied [468]. 

To increase the surface area of the stationary phase for CEC separation, a collocated monolithic support structure (COMOSS) was constructed in a Si chip. A polystyrene-sulfonic acid stationary phase was then immobilized [349]. Design of the COMOSS required that the combined cross sectional area at the column head to be the same at any point in the inlet distributor [644]. A study for the reduction of band broadening in COMOSS was also reported [645]. 

Sulfonamides may be directly synthesized from sulfonic acid salts by treatment with triphenylphosphine ditriflate followed by an amine <2004JA1024>. This procedure, that avoids the generation of sulfonic acids, converts sulfonic acid salt 129 to sulfonamide 130 in 81% yield (Equation 92). Problems associated with the removal of triphenylphosphine oxide by-products can be alleviated by performing the reaction with polystyrene-supported phosphine. 

The pioneer work in this field was carried out on polystyrene-supported acid catalysts [161]. Thereafter, several works on the use of sulfonic, strong acidic cation exchangers as acid catalysts were reported for alkylation, hydration, etherification, esterification, cleavage of ether bonds, dehydration, and aldol condensation [162,168-171], Besides, industrial applications of these materials were evaluated with reactions related to the chemistry of alkenes, that is, alkylation, isomerization, oligomerization, and acylation. [163,169], Also, Nation, an acid resin which has an acid strength equivalent to concentrated sulfuric acid, can be applied as an acid catalyst. It is used for the alkylation of aromatics with olefins in the liquid or gas phases and other reactions however, due to its low surface area, the Nation resin has relatively low catalytic activity in gas-phase reactions or liquid-phase processes where a nonpolar reactant or solvent is employed [166],... 

FIGURE 18 / 0 0 A heterocycle-release strategy was [433] applied to solid-supported a-tosyloxy ketones in the synthesis of a pentasubsti-tuted pyrrole. Sulfonic acid resin, prepared from commercially available sulfo-nyl chloride resin or polystyrene, was employed. 

Of course, only relatively low levels of sulfonic acid functionalisation have been studied on the silica supports in this work, and it could be argued that a fair comparison requires higher levels of sulfonation to be included. However, it is extremely difficult to functionalise silica at the sort of level achievable readily with polystyrene, so such a comparison is not possible. 

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