P-Toluenesulfonic acid as catalyst

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... 

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... 

Fortunately, the reactivity levels of the two ketone carbonyls in 32 were sufficiently disparate to permit selective ketalization of that located on the pendant chain. The conversion to 33 was achieved in good yield by means of trimethyl orthoformate in excess methanol with p-toluenesulfonic acid as catalyst. Subsequent exposure of this... 

Reaction of butane-1,2,4-triol 28 1 with acetone and p-toluenesulfonic acid as catalyst for 62 h gives a thermodynamic mixture of isopropylidene derivatives consisting of the dioxolane 28.2 (90%) and the dioxane 283 (10%) in a com-... 

Phenolic esters are obtained similarly. The presence of a nitro group in the aromatic nucleus and the use of pyridine as solvent facilitates the reaction. This reaction is recommended for the characterization of phenols. 2,4,5-Trichlorophenyl-, pentachlorophenyl-, 4-nitrophenyl- and thiophenyl esters of N-acylamino acids are prepared in this manner. These aromatic esters are used in the stepwise lengthening of peptides, du Vigneaud and coworkers synthesized lysine vasopressin from a nonapeptide which they prepared stepwise using the nitrophenyl ester method. Room temperature esterification of dicarboxylic acids and diphenols are also carbodiimide mediated using the 1 1 complex derived from DMAP and p-toluenesulfonic acid as catalyst Methacrylic acid is also esterified with phenols using carbodiimides and DMPA to mediate the reaction. ... 

OR 2,6-Norbornanediol. This polymer was prepared by a procedure similar to that for cyclohexanedimethanol using p-toluenesulfonic acid as catalyst. After concentration of a portion of the benzene solution, a polymer with an inherent viscosity of 0.28 was obtained. When the benzene solution was poured into methanol, a semisolid product was obtained. After being dried, the product, a clear, brittle resin, had an inherent viscosity of 0.49. Its melting range and solubilities are given in Table I. 

The use of this reaction has been confined almost entirely to the synthesis of phenolic glycosides, by fusion of the phenol with the 0-acetylated sugar in the presence of anhydrous zinc chloride or p-toluenesulfonic acid as catalyst the former favors the formation of the a and the latter of the /3 anomerA Improved yields result from the removal, under diminished pressure, of the acetic acid produced in the reaction, as well as of any that may be added. ... 

Use as acid catalyst. This acidic ester is superior to p-toluenesulfonic acid as catalyst for the preparation of 2, 3 -0-isopropyIidene (acetonide) and other ketal derivatives of ribonucleosides, for example of adenosine (3). A mixture of the nucleoside, acetone, the catalyst, and 2,2-dimethoxypropane (which serves as... 

Helferich method. Glycosidation of an acety-lated sugar by heating with a phenol in the presence of zinc chloride or p-toluenesulfonic acid as catalyst. 

Intermolecular reactions of species (69) with simple alkenes have received little attention. Recently, a study of the reaction of 5-ethoxy-2-pyrrolidinone with several 1,3-dienes in the presence of acid was published. When a mixture of ethoxylactam and 2,3-dimethylbutadiene is stirred in neat formic acid, the formates (73) and (74) are isolated as the main products in 43% yield. The bicyclic product (75) is obtained in only 16% (equation 38). If the reaction is carried out in benzene with p-toluenesulfonic acid as catalyst (75) is formed in 19% yield. Other dienes show similar behavior, producing bicyclic compounds as byproducts in low to moderate yields except for one or two cases, as illustrated with com-... 

Aromatic nitriles may be trimerized at moderate temperature and pressure with p-toluenesulfonic acid as catalyst. Studies were conducted to establish the effect of the reaction temperature, pressure, time, and catalyst concentration on yield of the trimerized product. Trimerization studies were also conducted to establish the effect of substituting electron donating or withdrawing groups on benzonitrile. Preliminary results of using the catalytic trimerization approach to prepare s-triazine cross-linked polyimide/graphite fiber composites are presented. 

In the second approach, treatment of lactoside derivatives 19 and 63 with benzaldehyde dimethylacetal in dry acetonitrile using p-toluenesulfonic acid as catalyst gave the 4, 6 -0-benzylidene derivatives 66 and 67 in 93% and 89% yield, respectively. Further derivatization of 23 (Scheme 4) was also considered in order to prepare sialyl Le as shown in Scheme 15. The disarmed-latent trisaccharide acceptor 23 was first coupled with ethylthio fucopyranosyl donor 57 in the presence of NIS/TfOH in dichloromethane at —70°C to give sialylated tetrasaccharide 70 in 63% yield together with recovered trisaccharide acceptor 23 (17%) and a minor unidentified regioisomer (less than 10%) (Scheme 15). 

Migration of the carbon-carbon double bond can be prevented by using the weak adipic acid in place of p-toluenesulfonic acid as catalyst.—E Cortisone 21-acetate cortisone 21-acetate Zl -3-ethyleneketal. Y 74%. F. e. s. J. J. Brown, R. H. Lenhard, and S. Bernstein, Experientia 18, 309 (1962). 

Dioxolanes are prepared by cyclocondensation of aldehydes or ketones with 1,2-dioles in benzene and with p-toluenesulfonic acid as catalyst ... 

Monomers Macrocyclic formals was synthesized from fractionally distilled polyethylene glycol and paraformaldehyde using p-toluenesulfonic acid as catalyst by the similar method in the literature (14). They were purified and dried by distillation over lithium aluminum hydride for four times. The purity was checked by gas chromatography. 

The glucuronide (26) of the new oral antidiabetic agent CS-04S has been synthesized by use of the /3-glyco l acetate together with p-toluenesulfonic acid as catalyst, and a report on the O- and iV-linked glucosides (27) and (27a) of an aromatic amino-acid has appeared. ... 

A soln. of tetralin-p-quinol acetate in glacial acetic acid treated with a satd. soln. of 2,4-dinitrophenylhydrazine in glycol monomethyl ether, and allowed to stand 24 hrs. at room temp. 2,4-dinitrobenzeneazo-6-tetralin. Y 96%. E. Hecker, B. 92, 1386 (1959) also with p-toluenesulfonic acid as catalyst s. B. 92, 3198. 

---