Sulphonate esters reactivity

This sequence serves to exemplify the formation and aspects of reactivity of toluene-p-sulphonate esters in monosaccharide systems, and further to illustrate the selective protection afforded to hydroxyl groups by the formation of cyclic acetals by reaction with carbonyl compounds. Thus reaction of methyl a-D-glucopyranoside (26) with benzaldehyde in the presence of zinc chloride gives the 4,6-acetal (27) (Expt 5.118), wherein two fused six-membered rings of the frans-decalin type are present. As a cognate preparation the reaction of benzaldehyde with methyl a-D-galactopyranoside results in a similar conversion to a 4,6-acetal, but in this case the product is the conformationally flexible system of the cis-decalin type, the most likely conformation being that shown below. 

Figure 5.5 Effect of reaction medium on the relative reactivity of hydroxyl and bromide ions with a lipophilic sulphonate ester.

Earlier, it was shown that sulphenes, formed by reaction of sulphonyl halides with a base, reacted with alcohols to give sulphonate esters. These same reactive intermediates have also been used for the formation of sultones, by reaction with carbonyl-containing compounds424-428, as shown in equation 98. If the carbonyl compound contains an a-... 

While the available literature only describes the electronic activity of organic arenesulphinates, it should be assumed that esters 1 can undergo cathodic reduction only when R and/or R possess a rather low energy level of their LUMO. In other words, when R and R are fully saturated, it is rather foreseeable that 1 is totally inactive in terms of cathodic reactivity. To the best of our knowledge, all papers devoted to sulphonic esters deal only with the behaviour of arenesulphonates4 and nearly all of them focus their interest on the reduction of tosylates 2 (R" = p-CH3). 

Many synthetically useful procedures have been developed15 since it was established16,17 that the reactivity of sulphonate esters (ZS020R) depends strongly on the substituent (Z) for instance, because triflates (Z = CF3) are much more reactive than tosylates, they permit solvolytic generation of aryl cations (2) from activated aryl esters (l)18, nucleophilic aromatic substitution catalysed by metal complexes (equation 5)19,20... 

The determination of the Arrhenius parameters for the alkaline hydrolysis of a series of sulphonate esters (Table 2) shows that the reactivity difference in sulphonates arises from a combination of entropy and enthalpy effects, although the latter is likely to be the dominant factor156. The different mechanism of hydrolysis (ElcB) of phenyl toluene-a-sulphonate 43 shows up clearly in the anomalous value of AS. ... 

Sulphonyl Peroxides.—Continuing interest in this class of compound is a consequence of their value in aromatic sulphonoxylation and in their addition to alkenes to give sulphonate esters. A useful electrochemical preparation of bis(methanesulphonyl) peroxide from sodium methanesulphonate makes available a reagent for the synthesis of methanesulphonates of less reactive aromatic hydrocarbons. 

The chemistry of a-haloketones, a-haloaldehydes and a-haloimines Nitrones, nitronates and nitroxides Crown ethers and analogs Cyclopropane derived reactive intermediates Synthesis of carboxylic acids, esters and their derivatives The silicon-heteroatom bond Syntheses of lactones and lactams The syntheses of sulphones, sulphoxides and cyclic sulphides... 

The extremely attractive bright blue hue combined with excellent light fastness of Cl Reactive Blue 19 (7.37) remained unchallenged by competing blue reactive dyes for many years. The aqueous solubility of this structure is inherently low, depending only on the 2-sulphonate group after 1,2-elimination of the sulphate ester has taken place. This has led to... 

Metabolites formed during the decolourization of the azo dye Reactive red 22 by Pseudomonas luteola were separated and identified by HPLC-DAD and HPLC-MS. The chemical structures of Reactive red 22 (3-amino-4-methoxyphcnyl-/fhydroxyl-sulphonc sulphonic acid ester) and its decomposition products are shown in Fig. 3.92. RP-HPLC measurements were carried out in an ODS column using an isocratic elution of 50 per cent methanol, 0.4 per cent Na2HP04 and 49.6 per cent water. The flow rate was 0.5 ml/min, and intermediates were detected at 254 nm. The analytes of interest were collected and submitted to MS. RP-HPLC profiles of metabolites after various incubation periods are shown in Fig. 3.93. It was concluded from the chromatographic data that the decomposition process involves the breakdown of the azo bond resulting in two aromatic amines [154],... 

Fig. 3.93. The HPLC analysis on metabolites resulting from decolourization of reactive red 22 by Pseudomonas luteola (a) at the beginning of static incubation (IA = 3 639 667, /B = 130 140, Ic 116 243), (b) after static incubation for 4.7 h (/A = 2 231 542, /B = 230 559, Ic = 120 563), (c) after static incubation for 23.4 h (/A = 1 892 854, /B = 428 414, Ic = 205 169), (d) 3-amino t-methoxyphenyl /1-hydroxyl sulphone sulphonic acid ester (AMHSSAE), 90 per cent pure, 52 mg/1, and (e) products resulting from decolourization of Reactive red 22 by chemical reduction with SnCl2, (/A, /B, and 7C represent intensities of peaks A, B, and C, respectively). Reprinted with permission from J.-S. Chang et al. [154].

Methylenesulphones are more acidic than the simple esters, ketones and cyano compounds and are more reactive with haloalkanes [e.g. 48-57] to yield precursors for the synthesis of aldehydes [53], ketones [53], esters [54] and 1,4-diketones [55] (Scheme 6.4). The early extractive alkylation methods have been superseded by solidtliquid phase-transfer catalytic methods [e.g. 58] and, combined with microwave irradiation, the reaction times are reduced dramatically [59]. The reactions appear to be somewhat sensitive to steric hindrance, as the methylenesulphones tend to be unreactive towards secondary haloalkanes and it has been reported that iodomethylsulphones cannot be dialkylated [49], although mono- and di-chloromethylsulphones are alkylated with no difficulty [48, 60] and methylenesulphones react with dihaloalkanes to yield cycloalkyl sulphones (Table 6.5 and 6.6). When the ratio of dihaloalkane to methylene sulphone is greater than 0.5 1, open chain systems are produced [48, 49]. Vinyl sulphones are obtained from the base-catalysed elimination of the halogen acid from the products of the alkylation of halomethylenesulphones [48]. 

Covalent bonds. The covalent bond between carbon atoms in most organic compounds is very stable. It has been realized for a long time that great wet fastness would be obtained if dye molecules could be anchored to textile fibres by covalent bonds. During the last decade this has been achieved with the aid of certain reactive groups such as cyanuryl chloride, trichloropyrimidyl, sulphonethanolamide sulphuric acid ester, and vinyl sulphone. 

Various types of surface-anchor interactions are responsible for the adsorption of a dispersant to the particle surface. These include ionic or acid/base interactions sulphonic acid, carboxylic acid or phosphate with a basic surface (e.g., alumina) amine or quaternary with an acidic surface (e.g., silica) H-bonding surface esters, ketones, ethers, hydroxyls multiple anchors-polyamines and polyols (H-bond donor or acceptor) or polyethers (H-bond acceptor). Polarizing groups (e.g., polyurethanes) can also provide sufficient adsorption energies and, in nonspecific cases, lyophobic bonding (via van der Waals attractions) driven by insolubility (e.g., PMMA). It is also possible to use chemical bonding, for example by reactive silanes. 

Other reactive halides employed include butyl iodide to yield butyl esters with, for example, the silver salts of methane- and ethanesulphonic acids106 or p-nitrobenzyl chloride or bromide, reacting in pyridine solution with sulphonates to yield addition product with pyridine molecules107. Classifiable here also is conversion to trimethylsilyl derivatives with bis (trimethylsilyl) trifluoroacetamide108. 

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