P-Toluenesulfonic acid, catalysis

It has also been shown that XIII is converted into XIV and vice versa upon contact with triflic acid in acetonitrile, thus strongly suggesting the intermediacy of the bicyclic structure in the route that leads to XIV and III. Its intermediate precursor XII would also be amenable to fragmentation to give carbocation XVI that obviously precedes carbinol XV. Finally, the slow conversion of the latter to XIV under p-toluenesulfonic acid catalysis has also been observed. 

Enamines formed in this way may be distilled or used in situ. The ease of formation of the enamine depends on the structure of the secondary amine as well as the structure of the ketone. Thus pyrrolidine reacts faster than morpholine or piperidine, as expected from a rate-controlling transition state with imonium character. Six-membered ring ketones without a substituents form pyrrolidine enamines even at room temperature in methanol (20), and morpholine enamines are generated in cold acetic acid (21), but a-alkylcyclohexanones, cycloheptanone, and linear ketones react less readily. In such examples acid catalysis with p-toluenesulfonic acid or... 

Under the catalysis of mercury(II) oxide and p-toluenesulfonic acid, allenic /8-keto esters 43 and 45 afforded the furan derivatives 44 and 46 [27]. 

More synthetic interest is generated by the potentially very useful hydration of dienes. As shown on Scheme 9.6, methylethylketone (MEK) can be produced from the relatively cheap and easily available 1,3-butadiene with combined catalysis by an acid and a transition metal catalyst. Ruthenium complexes of several N-N chelating Hgands (mostly of the phenanthroline and bipyridine type) were found active for this transformation in the presence of Bronsted acids with weakly coordinating anions, typically p-toluenesulfonic acid, TsOH [18,19]. In favourable cases 90 % yield of MEK, based on butadiene, could be obtained. 

We believe that catalysis occurs by formation of a complex between acetaldehyde, peracetic acid, and the metal ion in the 3+ oxidation state. The metal ion could be acting as a superacid as for peracetic acid decomposition, although oxidation-reduction reactions within the complex cannot be ruled out. Here again, we have found a disturbing lack of catalytic activity of other trivalent metals (aluminum, iron, and chromium). Simple acid catalysis is not as effective as proved when using p-toluenesulfonic acid and acetyl borate. This indicates that at least more than one coordination position is needed to obtain a complex of the proper configuration. 

Propargylic alcohols, even though tertiary (1), react with dihydropyrane under catalysis from p-toluenesulfonic acid to give tetrahydropyranyl derivatives (2), which are stable to base but hydrolyzed readily by aqueous acid or magnesium sulfate. ... 

Mol. wt. 142.15, m.p. 13°, b.p. 65-67°/0.2 mm. Formed by reaction of diketene with acetone under catalysis by p-toluenesulfonic acid. Supplier Aldrich. 

Synthesis of fi-ketoallenes and a,fi-unsaturated ketones.1 Isopropenyl methyl ether, under acid catalysis (p-toluenesulfonic acid or phosphoric acid particularly), reacts with a tertiary acetylenic carbinol to give a/3-ketoallene in high yield, as exemplified by the reaction with 3 methylbutyne-l-ol-3 (1). The /3-ketoallene (2) is... 

Protection of a hydroxyl group.1 Like dihydropyrane, the reagent adds an alcohol under catalysis by p-toluenesulfonic acid to give a ketal (4), but it has the advantage that a new asymmetric center is not introduced. The ketal system is very labile to dilute acid. The reagent has been used for hydroxyl group protection in oligoribo-nucleotide synthesis. 

Ribonucleoside 2 J -orthocarbonates. Under acid catalysis (p-toluenesulfonic acid) ribonucleosides (1) undergo exchange with tetramethyl orthocarbonate (excess) in anhydrous dioxane solution to give 2, 3 -0-dimethoxymethylidene derivatives (2) in 50-80% yield. The derivatives are converted by mild acid treatment (98% formic acid) into 2, 3 -carbonates (3). The sequence may have useful... 

Ynamines are the only nucleophilic dienophiles reactive enough to give a [4 -I- 2] cycloadduct with 2.4,6-tris(methy]sulfanyl)-l,3,5-triazine (9, R1 = SMe). The initial cycloadducts are stable and isolable and the following pyrimidine generation can be achieved thermally (150-230 °C) or by acid catalysis (p-toluenesulfonic acid, 100 °Q. Enamines and electron-deficient dienophiles fail to react with this triazine derivative.6... 

The third approach was based on cyclodehydratation of 6-aroylhydrazido-purine derivative 278 under catalysis by p-toluenesulfonic acid giving rise to tricyclic 279. The necessary intermediate 278 was accessible easily by transformation of the 6-methylthio derivative 277 by, e.g., isonicotinoyl hydrazide. Compounds 279 are stable in acid in contrast to parent triazolopurines 274 (X = H). Notable is their bronchodilatation effect, up to 100 x greater than that of theophylline (92TL3151) (Scheme 80). 

MMTS MsOH NBS NHMDS NMP NMR PPb Ph Pr PTC rt TBDMS Tf THF THP TLC TMEDA TMS TMSOTf Tol TOMAC Ts TsOH UDP methyl methylthiomethyl sulfoxide (=FAMSO) methanesulfonic acid N-bromosuccinimide sodium hexamethyldisililazide /V-methyl-2-pyrrolidone nuclear magnetic resonance parts per billion phenyl propyl Phase transfer catalysis room temperature t-butyldimethylsilyl triflatc (trifluoromethanesulfonate) tetrahydrofuran 2-tetrahydro-2//-pyran-2-yl thin-layer chromatography /V./V./V /V -tetramethylethylenediamine trimethylsilyl trimethylsilyl triflate p-tolyl trioctylmethylammonium chloride tosyl p-toluenesulfonic acid ultrasonically dispersed potassium... 

Transacetalization. The reagent is effective for transacetalization. The reaction is carried out at 20° in chloroform with catalysis by p-toluenesulfonic acid or by slightly wet BF3 etherate. Anhydrous BF3 etherate is ineffective. 

A number of control reactions were carried out in order to assess the importance of the individual components of TBA3H2I. First, a model (Table I, entry 2) of the active catalyst comprising TBA4Fe(H20)PWn039, TBANO3 and a proton source (p-toluenesulfonic acid, pTsOH) in the same mole ratios to entry 1 was evaluated. The catalytic activity of this model system is similar to that of the active catalyst. Upon removal of the POM from the system, the catalytic activity is lower (entry 3). The addition of a proton-specific base, 2,6-di-r-butylpyridine, to the active catalyst, TBA3H2I, results in complete loss of activity (entry 4). Other NOx species (including, but not limited to, entries 5 and 6) show minimal activity. Thus, all components of the reactive system, POM, nitrate, and proton, are essential for optimal catalysis of eq 1. 

A direct method for the identification of the alcoholic component of esters consists in the reaction of the ester with 3,5-dinitrobenzoyl chloride in pyridine. In the case of simple esters (51) the reesterification can be carried out by heating the tested ester with 3,5-dinitrobenzoic acid under catalysis with sulfuric or p-toluenesulfonic acid. 

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