Arylsulfonic acids, synthesis

Instead of the isolated arylsulfonic acid azolides, mixtures of arylsulfonic acid chlorides and azoles have also been used for phosphorylation on a nucleoside 5 -OH or as coupling agents in the synthesis of oligodeoxyribonucleotides. 94 133 1371... 

Lactonization of a h>e-unsaturated ester In a projected synthesis of quassinoid diterpenes, the final step involves lactonization of the unsaturated ester 1. Acid-catalyzed solvolysis (HC1 in THF) or treatment with an arylsulfonic acid in toluene results mainly... 

These zirconium phosphate materials are being developed as replacements for ion exchange resin catalysts. The arylsulfonic acid MELS have been evaluated for butene isomerization, methanol dehydration, MTBE synthesis as well as cracking, and for the alkylation of aromatics. In the synthesis of MTBE this catalyst appears to out-perform the ion exchange resins, Amberlyst 15. 

In the synthesis of arylsulfonyl chlorides, it is generally preferable to add the aromatic substrate gradually to the excess of chlorosulfonic acid rather than the other way about. Under these conditions, the reagent is mostly present in a large excess during the reaction which minimizes the formation of both the diaryl sulfone and the arylsulfonic acid. With highly reactive substrates, an inert solvent is used and the reaction temperature must be carefully controlled and kept as low as feasible to avoid unwanted di- and trisulfonation. ... 

Sulfonic acid groups (SO3H) are both bulky and electron-withdrawing consequently once one sulfonic acid group has been introduced into the aromatic nucleus, the resultant arylsulfonic acid will be more resistant towards further sulfonation. The latter will require more drastic conditions and the product will contain the two sulfonic acid groups in the 1,3-position with respect to each other. With reactive substrates, e.g. aromatic hydrocarbons, halides or ethers, mono-chlorosulfonation is often best achieved at low temperature in ftie presence of chloroform, dichloromethane or 1,2-dichloroethane to moderate the reaction and avoid disulfonation. Suter and Weston S described the experimental procedures for the sulfonation of aromatic hydrocarbons, halides and ethers and many early references and details of the synthesis of sulfonic acids and sulfonyl chlorides are included in Suter s comprehensive text." ... 

Peptides and amino acids may be sulfated the hydroxyl groups of serine and threonine reacted with chlorosulfonic acid in trifluoroacetic acid to give the O-sulfate esters. The free amino groups did not react since they were completely protonated in the strongly acidic media and the rates of sulfonation were determined. Peptides containing the above amino acids were also sulfated. The aromatic amino acids tyrosine and tryptophan, by treatment with chlorosulfonic acid-trifluoroacetic acid, afforded the arylsulfonic acid derivatives. In the solid phase synthesis of cholecystokinin-33, tyrosine has been sulfated to the O-sulfate with chlorosulfonic acid and this was incorporated into the peptide sequence. ... 

Tetravalent metal phosphonates (MELS ) are layered compounds that can be considered organic/inorganic polymers. The organic functionality provided by the phosphonate largely determines the surface chemistry of these materials. Choosing phosphonates with an arylsulfonic acid function produces materials that are effective as acid catalysts. This paper describes synthetic procedures used to prepare arylsulfonic acid MELS and methods to increase and stabilize their surface area, porosity, and swelling properties. Acid catalysis by MELS is exemplified by the synthesis of methyl tertiary butyl ether. 

Comparative performance of arylsulfonic acid-based catalysts for MTBE synthesis. 

We evaluated the catalytic performance of the arylsulfonic acid MELS in a number of reactions, including isomerization of butenes, MTBE synthesis, methanol dehydration, aromatic alkyMon, and MTBE cracking. An example of its utilization as a catalyst for MTBE synthesis follows. 

Saito et al. [33] described a new method for the synthesis of heterocycle-fused[c]thiophenes via reaction of aryl heteroaryl thioketones with carbene precursors. Heteroaromatic thioketones A react with carbenoids generated from bis(arylsulfon yl)diazomethanes or phenyliodonium bis(phenylsulfonyl)methylides to give hete-rocycle-fused[c]thiophenes B (Scheme 20). The reaction involves the ring closure of the intermediary thiocarbonyl ylides, followed by restorative aromatization via the elimination of a sulfenic acid. The present method provides simple and facile access to a variety of furo- 118, benzofuro- 119, thieno- 120, benzothieno- 121, pyrrolo-122, and indolo-123 fused [c]thiophenes (Scheme 20). 

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