P-toluensulfonic acid

De Groot et al. synthesized ( )-3(3-hydroxynagilactone F (54) [85] from compound 172 [86] with an overall yield of 0.2% (13 stages). The key steps in this synthesis were the formation of the 5-lactone by nuclelophilic addition to carbonyl and subsequent treatment with p-toluensulfonic acid, the introduction of the isopropyl in an a equatorial disposition following a procedure similar to that described by Hayashi et al. and finally the formation of the y-lactone via bromolactonization. 

Dihydro-4-hydroxy-2-(2-methoxy)ethyl-2H-thieno[3,2-e]-l,2-thiazine 1,1-dioxide (4.9 g, 50 18.6 mmol) was converted to the 4-(l-ethoxy)ethoxy-3,4-dihydro-2-(2-methoxy)ethyl-2H-thieno[3,2-e]-l,2-thiazine 1,1-dioxide (6.2 g, 99%) using the reaction with p-toluensulfonic acid and ethylvinyl ether at 0°C in tetrahydrofuran for 2 hrs. 

A solution of 92.6 mmol (12.8 g) 4-methoxybenzyl alcohol, 2.25 mmol nitroxyl radical 6, 4.5 mmol p-toluensulfonic acid, 1.8 mmol Mn(N03)2, and 1.8 mmol Cu(N03)2 in 100 mL CH3COOH was stirred at r.t. for 3h under air at atmospheric pressure. The CH3COOH was then evaporated at ca. 55 torr and the reaction product was extracted with methyl-t-butyl ether (the salt of the nitroxyl radical 6 with p-toluensulfonic acid, can be recovered and recycled). GC analysis (4-methylbenz-... 

It is worth of note that the formation of a dimer, with different dioxane structure, in the treatment of 3,4-dihydroxyprecocene I with p-toluensulfonic acid has been recently reported (13). Further work, to study the reactivity of precocene epoxides with selected nucleophiles, which can shed light on the mode of action of these compounds, is in progress. 

One of the most commonly used acid catalysts in organic reactions is p-toluensulfonic acid (PTSA). This acid was used to evaluate the possibility of selfcondensation of MAGME -polymers. Thick (20 ym) films were coated on glass plates and cured in an oven at different temperatures and curing times. Data in Table 2 show the time required at lowest possible curing temperature. In the case of PTSA it was difficult to achieve curing at temperatures below 120 C. This, and the fact that it took nearly... 

SCHEME 6. Synthesis of trisaccharide 18. Conditions (i) a-a-dimethoxytoluene, p-toluensulfonic acid,... 

Scheme 13 Reduction of tetralone (127) with sodium borohydride afforded alcohol, which was benzylated to obtain the derivative (132), which on treatment with boron tribromide in dichloromethane yielded this diol (134) in major proportion. It was converted to compound (136) by treatment with triethyl orthoformate and then catalytic hydrogenation. Oxidation of (136 and on subjection of the resulting ketone with methylmagnesium bromide followed by heating with p-toluensulfonic acid in toluene produced compound (129).

Substituted analogs are converted to these cyclic trimers in fair yield by p-toluensulfonic acid in CH2CI2 [188, 189]. The trimer is also formed under basic condition from 3-(trimethylammonio-methyl)indole [190]. This method also gives rise to some of the isomeric tetramer. 

Another study suggested the use of other sulfonating agents such as p-toluensulfonic acid (p-TSA). Although the material seems to be very efficient catal3ftically, its activity looks to be more related to the residues of p-TSA on the material than to attached sulfonic groups, because the analysis of the sample showed bands in the infrared spectra associated specifically to p-TSA. This would be likely to leach into solution. Another drawback of this approach is related to the manner of preparing p-TSA, as precursors involved will be toluene (petroleum base material) and sulfuric acid. 

In the framework of this research topic, PPy chains self-assembled in nanowires with a coral-like shape can be obtained by FeCb induced oxidative polymerization and dodecil-benzenic sulphonic acid (DBSA) dopant [106] oxidative polymerization is a widely used method for the attainment of polymeric nanostructures. For example, bundles of self-assembled PPy nanotubes have been fabricated by polymerization reaction with bis(2-ethylhexyl) sulfosuccinate reverse (water-in-oil) emulsions [107] and rods with enhanced electrical conductivity and thermal stability are reported to be formed via a self-assembly process of micelle obtained from a oxidative polymerization in the presence of p-toluensulfonic acid used as surfactant and doping agent [108, 109]. A further example of PPy nanotubes synthesized by oxidative polymerization in octane is reported in Fig. 1.7 [107]. 

Hydrogenation of 25 was accomplished using Pearlman s catalyst to provide amino-ester 28 as a 10 1 mixture of diastereoisomers favoring the desired cis isomer.Excess acid (>1 equiv of p-toluensulfonic or sulfuric acid) was necessary to facilitate the hydrogenation by promoting relatively rapid nitrile reduction to protonated amine 26. This protocol prevents catalyst deactivation. Acid also catalyzes the subsequent benzylic alcohol dehydration and the final reduction to 28. The observed increase in diastereoselectivity during the hydrogenation is consistent with acid-catalyzed elimination of water to form intermediate indene 27 followed by reduction from the least hindered face of 27 to afford the cis isomer of 28 as the major product. We did not observe elimination of water prior to nitrile reduction. ... 

A mixture of A-Boc-protected amino acid (5 mmol), 195 mg paraformaldehyde (6.5 mmol), and 43 mg /7-toluensulfonic acid (0.25 mmol) in 50 mL benzene was refluxed with the aid of a Dean-Stark trap, and heating was continued until no starting material was detected by TLC (1-3 h). The reaction mixture was cooled to room temperature, washed with 5% KHCO3 (2 X 30 mL) and brine (30 mL), dried, and concentrated. The crude product was purified by column chromatography or by crystallization from suitable solvents. For (45)-A-t rt-butyloxycarbonyl-4-methyl-l,3-oxazolidin-5-one from A-Boc-analine, 825 mg was obtained by crystallization from CH2Cl2-hexane as white needles, in a yield of 82%, m.p. 66-6TC. 

The solvolysis of 2i , 3S-3-(4-methoxyphenyl)but-2-yl p-toluensulfonate in acetic acid can be followed by several kinetic measurements (a) rate of decrease of observed rotation (fc ) rate of release of the leaving group (fc,) and, when O-labeled sulfonate is used, the rate of equilibration of the sulfonate oxygens... 

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