P-Toluenesulfonic acid , catalyst

Sardesai and Sunthankar studied the cyclization of diethyl )V-(2-amino-phenyl)aminomethylenemalonate (162, R = H) (57MI2 59MI1). No cyclization occurred in refluxing xylene in the presence or absence of a catalyst (p-toluenesulfonic acid or sodium hydroxide), or in acetic anhydride, or in a mixture of acetic anhydride and concentrated sulfuric acid. Benzimidazole and benzimidazolone were obtained in 20% and 66% yields, respectively, when 162 (R = H) was distilled in vacuo. Benzimidazolone was the product when 162 (R = H) was heated in boiling diphenyl ether, o-Phenylenediamine was reacted with diethyl acetylmalonate at 140°C for 4 hr to give 2-methylbenzimidazole and diethyl malonate (85S555). 

In the reaction of higher aldehydes employing hydrogen chloride or still another catalyst, p-toluenesulfonic acid, the water is conveniently removed by an azeotropic distillation with benzene. The vapors containing the ternary mixture of alcohol, benzene, and water are condensed in a water separator, and the benzene-alcohol mixture is automatically returned to the reaction flask either directly or after drying with calcium carbide. °... 

There exists currently only one mention in the literature of the synthesis of a heterohexaphyrin analog. This is the hexathiahexaphyrinogen species 7.20. This macrocycle was synthesized from 2-hydroxymethyl-3,4-diethylthiophene (7.19) by heating a nitromethane solution of this monomer to reflux in the presence of the acid catalyst p-toluenesulfonic acid. In addition to a cyclic tetramer and pen tamer (cf. Chapter 6), the cyclohexamer 7.20 could be isolated in yields ranging from 0.5% to 2% (Scheme 7.1.6). Unfortunately, it was not reported whether 7.20 could be oxidized to give the corresponding aromatic derivative. 

Annelation. 1,10-Dimethyl-1(9)-octalone-2 (2) has been prepared by the reaction of 2-methylcyclohexanone with the chloro ketone and an acid catalyst, p-toluenesulfonic acid or sulfuric acid. The acid presumably generates ethyl... 

Type of reaction C-N and C-C bond formation Reaction conditions Toluene, room temperature Synthetic strategy ElectrocycUc/sigmatropic rearrangement Catalyst p-Toluenesulfonic acid (PTSA)... 

Cyclic acetals are usually prepared by condensation of formaldehyde (conveniently in the form of paraformaldehyde or TOX) or higher aldehydes with diols in the presence of l-2wt.% of an acid catalyst p-toluenesulfonic acid or ion-exchange resins are most frequently used for this purpose (Scheme 4). ... 

Of the alkyl esters, methyl esters are the most useful because of their rapid hydrolysis. The acid is refluxed with one or two equivalents of methanol in excess alcohol-free chloroform (or dichloromethane) containing about O.lg of p-toluenesulfonic acid (as catalyst), using a Dean-Stark apparatus. (The water formed by the... 

Tetrahydropyranyl ethers are prepared by reaction with 2,3-dihydropyran, and a catalyst such as hydrochloric acid, " phosphorous oxychloride or p-toluenesulfonic acid at room temperature. 3iS-Hydroxy-5-enes " also form pyranyl ethers by distillation of a solution of the steroid and dihy-dropyran in ether without a catalyst. 

The general rule has been formulated (P) that the less substituted enamine is formed from unsymmetrical ketones such as the 2-alkylcyclohexanones. In enamine 21 the R, group and the N-alkyl groups would interfere with one another if overlap is to be maintained between the nitrogen unshared electrons and the double bond. There would be less repulsion if the isomeric enamine (22) were formed. 2-Phenylcyclohexanone and pyrrolidine with p-toluenesulfonic acid as catalyst in refluxing benzene gave enamine... 

A multitude of 1,4-dicarbonyls (1) undergo the Paal-Knorr reaction with and ranging from H to alkyl, aryl, carbonyl, nitrile, and phosphonate, while R and R vary between H, alkyl, aryl, trialkylsilyl, and O-alkyl. Protic acid catalysts are typically used with sulfuric, hydrochloric, and p-toluenesulfonic acids the most popular. Conversion to the furan takes place either at room temperature or upon heating with reaction times varying from five minutes to 24 hours and yields ranging from 17-100%. 

Raston has reported an acid-catalyzed Friedel-Crafts reaction [89] in which compounds such as 3,4-dimethoxyphenylmethanol were cyclized to cyclotriveratrylene (Scheme 5.1-57). The reactions were carried out in tributylhexylammonium bis(tri-fluoromethanesulfonyl)amide [NBu3(QHi3)][(CF3S02)2N] with phosphoric or p-toluenesulfonic acid catalysts. The product was isolated by dissolving the ionic liq-uid/catalyst in methanol and filtering off the cyclotriveratrylene product as white crystals. Evaporation of the methanol allowed the ionic liquid and catalyst to be regenerated. 

The acidic catalysts used for these reactions include formic acid, HX (X = F, Cl, Br), oxalic acid, phosphoric acid, sulfuric acid, sulfamic acid, and p-toluenesulfonic acid.4 Oxalic acid is preferred since resins with low color can be obtained. Oxalic acid also decomposes at high temperatures (>180°C) to C02, CO, and water, which facilitates the removal of this catalyst thermally. Typically, 1-6 wt % catalyst is used. Hydrochloric acid results in corrosive materials and reportedly releases carcinogenic chloromethyl ether by-products during resin synthesis.2... 

Resole resins are generally crosslinked under neutral conditions between 130 and 200° C or in the presence of an acid catalyst such as hydrochloric acid, phosphoric acid, p-toluenesulfonic acid, and phenolsulfonic acid under ambient conditions.3 The mechanisms for crosslinking under acidic conditions are similar to acid-catalyzed novolac formation. Quinone methides are the key reaction intermediates. Further condensation reactions in resole resin syntheses under basic conditions at elevated temperatures also lead to crosslinking. 

Esters of ether carboxylic acids (propylated and/or ethoxylated) and fatty alcohols or ethoxylated fatty alcohols are described [40], prepared by esterification of the ether carboxylic acid and the alcohol with an acid catalyst like H2S04 or p-toluenesulfonic acid under vacuum and at a temperature of about 130°C. The purpose of these esters is to mainly use them in cremes and lotions with better conditioning and moisture controlling properties. 

A new class of bicyclic oxalactam, 8-oxa-6-azabicyclo[3.2.1]octan-7-one 61 was synthesized by intramolecular cyclization of 3,4-dihydro-2H-pyran- 2-carboxamide 62 using p-toluenesulfonic acid as a catalyst in an equivalent mixture of DMF and benzene at 100 °C for 4 hours57, S8. Corresponding conversion of 3-cyclohexane carboxamide 63 to bicyclic lactam 64 has never been accomplished54. ... 

It is of primary interest to avoid corrosive mineral acids in synthetic processes. This can easily be achieved by use of acidic solid supports coupled with microwave irradiation. This has been applied to the preparation of quinolines [53] (Scheme 8.35). This procedure is a safe, green alternative to the use of H2S04 at more than 150 °C. In the same way, quinoxaline-2,3-diones were prepared [54] by use of single-mode irradiation. Previous attempts in solution led to explosions, but the authors successfully used solvent-free conditions with acidic supports or catalysts (the best being p-toluenesulfonic acid) and irradiation times of 3 min (Scheme 8.36). 

For 1,3,2,5-dioxaboraphosphorinanes with a tricoordinated phosphorus atom, equilibration of the stereoisomers has been observed after a few hours at 20°C without any catalyst. In the case of the sulfide and selenide the equilibrium is established in 11-20 h at 80°C in the presence of p-toluenesulfonic acid. The equilibrium composition of 2,5-diphenyl-4,6-... 

Brigl and Griiner45 reported the isolation of three products when 1,6-di-O-benzoyl-D-mannitol (29) was heated in boiling 1,1,2,2-tet-rachloroethane in the presence of p-toluenesulfonic acid as the catalyst. These compounds were assigned mono- and di-anhydro structures, and were later shown by Hockett and coworkers46,47 to be 1,4-anhydro-D-mannitol dibenzoate (30), l,4 3,6-dianhydro-D-man-nitol dibenzoate (31), and 2,5-anhydro-l,6-di-0-benzoyl-D-glucitol (32). The latter compound, which can be readily isolated from the... 

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