Toluene-p-sulphonates

Naphthalene, oxalic acid (hydrated), cinnamic acid, acetamide, benzamide, m-dinitrobenzene,/>-nitrophenol, toluene p-sulphon-... 

The toluene-p sulphon-dimethylamide can be readily hydrolysed by boiling under reflux with 70% sulphuric acid (see p. 107). If the... 

Phenyl Toluene-p-sulphonate. CH C iHaSO OC H (Semi-micro Scale.)... 

Toluene-p-sulphonchloro-sodio-amide ( Chloramine-T ), CHjC HjSO-NNaCh. H.O, and Toluene-p-sulphon-dichloro-amide ( Dickloramine-T ), CH3C H4S02Na2. 

The resins are hardened in situ by mixing with an acidic substance just before application. A typical curing system would be four parts of toluene-p-sulphonic acid per 100 parts resin. The curing may take place at room temperature if the resin is in a bulk form but elevated temperature cures will often be necessary when the material is being used in thin films or coatings. 

This trimer was then synthesised by refluxing the benzoxazole (LII) with toluene-p-sulphonic acid in benzene. In contrast, the cis-isomer of (LII) is stable under these conditions. The mechanism of formation of the trimer (LIII) was discussed (754). 

Intramolecular cyclization of cannabielsoin in benzene-toluene-p-sulphonic acid to the 1,8-cineol (264) is quantitative. The previously reported rearrangement... 

A stereoselective total synthesis of the antifungal mould metabolite ( )-LL-Z1271a (165) from the readily available Wieland-Miescher diketone, via the keto-lactone (164), has been described. A synthesis of grindelic acid (167) from the unsaturated 7-toluene-p-sulphonate (166) utilized an intramolecular solvolysis of the toluene-p-sulphonate to construct the 9—13 ether bridge. 

Thionyl chloride 103-6, Toluene-p-sulphonic acid Transition states,... 

The first general comment relates to the solvent system. In those cases where the electrolysis substrate does not exist in an aqueous-ethanolic or methanolic solution in a suitable ionic form, it is necessary to provide a solvent system of low electrical resistance which will dissolve the substrate, and also a supporting electrolyte whose function is to carry the current between the electrodes. Examples of such solvents are dioxane, glyme, acetonitrile, dimethylformamide and dimethyl sulphoxide supporting electrolytes include the alkali metal halides and perchlorates, and the alkylammonium salts (e.g. perchlorates, tetrafluoro-borates, toluene-p-sulphonates). With these electrolysis substrates, mass transfer to the electrode surface is effected by efficient stirring. 

Unless the reagent has been recently purchased it may contain substantial amounts of toluene-p-sulphonic acid. The most satisfactory procedure for the purification of the chloride involves dissolving it in the minimum amount of chloroform (about 2.5 ml per g) and diluting with 5 volumes of light petroleum (b.p. 40-60 °C), which precipitates impurities. The filtered solution is treated with decolourising charcoal, filtered and concentrated to small volume when colourless crystals of the pure reagent, m.p. 68 °C, are obtained these should be washed with chilled light petroleum (b.p. 40-60 °C). 

The hydrolysis of alkylmagnesium halides (Expt 5.3), and the hydrogenolysis of alkyl halides and of alkyl methane- or toluene-p-sulphonates (Expt 5.4). 

Superhydride has also been used for the hydrogenolysis of alkyl toluene-p-sulphonates, and an illustrative example is given in Expt 5.4 for the preparation of cyclooctane from cyclooctyl toluene-p-sulphonate. A sodium borohydride hydrogenolysis of alkyl halides and of alkyl methane- and toluene-p-sulphonates under PTC conditions provides an interesting variant of this reaction.9... 

Notes. (1) A procedure for the preparation of alkyl toluene-p-sulphonates is described in Expt 6.46. 

An alternative deprotection method, which proceeds without prior isomerisation, involves heating under reflux the allyl ether in aqueous methanol with palladium/activated charcoal in the presence of toluene-p-sulphonic acid.79... 

Tetrahydropyranyl ethers, THP-ethers, are formed by reaction of an alcohol with 2,3-dihydropyran in the presence of an acid catalyst. The procedures below illustrate the use of concentrated hydrochloric acid or pyridinium toluene-p-sulphonate. Amberlyst H-15 resin has also been used as a reaction catalyst.81... 

The alcoholic hydroxyl group may be protected by conversion into, for example, the acetate, benzoate, p-nitrobenzoate, or toluene-p-sulphonate esters. Suitable specific and general procedures are described in Expts 5.142, 6.46, 6.163 and in Section 9.6.4, p. 1241. Esters may be hydrolysed under basic or acidic conditions, suitable procedures are described in Section 9.6.17, p. 1266. 

Procedure for 1,3-dioxolane formation with ethyl acetoacetate by azeotropic removal of water.128a Ethyl acetoacetate (30 g, 0.23 mol), ethane-1,2-diol (16g, 0.248 mol), a crystal of toluene-p-sulphonic acid and benzene (50 ml) (CAUTION) were placed in a round-bottomed flask fitted with a Dean and Stark water separator (Fig. 2.31(a)) and a reflux condenser. The reaction mixture was heated until no more water collected. The product was fractionally distilled under reduced pressure to give the cyclic acetal (35 g, 87%), b.p. 99.5-101 °C/17-18 mmHg. 

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. 

Deprotection is effected in the case of methyl or ethyl esters by hydrolysis, usually under basic conditions (Section 9.6.17, p. 1266). t-Butyl esters are de-protected by mild acidic conditions, for example, formic acid at room temperature,159 toluene-p-sulphonic acid in benzene solution, or hydrogen bromide in acetic acid at 10°C.160... 

A recent procedure for the preparation of methyl esters involves refluxing the carboxylic acid with methanol and 2,2-dimethoxypropane in the presence of toluene-p-sulphonic acid as the catalyst (Expt 5.146). The water produced in the esterification process is effectively removed by acid-catalysed reaction with the ketal to give acetone and methanol. 

In a 500-ml single-necked flask containing a magnetic stirrer bar, place 58.5 g (0.4 mol) of adipic acid, 16 g (20 ml, 0.5 mol) of methanol, 83.2 g (0.8 mol) of 2,2-dimethoxypropane and 0.5 g of toluene-p-sulphonic acid. Fit a reflux condenser to the flask and stir the mixture magnetically for 4 hours in a water bath kept at 45 °C. Rearrange the condenser for distillation and distil off acetone (b.p. 56 °C) and methanol (b.p. 64 °C) on the water bath. Distil the residue under reduced pressure (water pump) and collect the dimethyl adipate, b.p. 130°C/25mmHg. The yield is 54.9 g (79%). 

The Grignard reagent derived from benzyl chloride undergoes ready alkylation with an alkyl toluene-p-sulphonate, a reaction which provides a further useful synthesis of an alkylbenzene (e.g. pentylbenzene, Expt 6.2). 

The sulphonation of toluene (Expt 6.37) with concentrated sulphuric acid at 100-120°C results in the formation of toluene-p-sulphonic acid as the chief product, accompanied by small amounts of the ortho and meta isomers these are easily removed by crystallisation of the sodium salt of the para isomer in the presence of sodium chloride. Sulphonation of naphthalene at about 160°C yields largely the 2-sulphonic acid (the product of thermodynamic control) (Expt 6.38) at lower temperatures (0-60 °C) the 1-sulphonic acid (the product of kinetic control) is produced almost exclusively. In both cases the product is isolated as its sodium salt. In anthraquinone the carbonyl groups deactivate the aromatic nucleus towards electrophilic attack and vigorous conditions of sulphonation are required, i.e. oleum at about 160 °C. The product is largely sodium anthraquinone-2-sulphonate (Expt 6.39). 

The free sulphonic acids [e.g. toluene-p-sulphonic acid, for preparation see, Expt 6.37, Note (1)], as opposed to their sodium salts, may sometimes be obtained directly if the sulphonation reaction is carried out with continuous removal of the water formed in the reaction, conveniently by using a Dean and Stark water separator. p-Xylene-2-sulphonic acid (Expt 6.40) is an example of a sulphonic acid whose solubility in water is such that it crystallises directly from the reaction medium and hence it may readily be isolated. 

Experiment 6.37 SODIUM TOLUENE-p-SULPHONATE AND TOLUENE-p-SULPHONIC ACID... 

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