Pyridinium toluene-p-sulphonate

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... 

Ethers, Esters, and Related Derivatives of Alcohols.—5a-Cholestanyl methyl ether has been cleaved inter alia) and converted into 5a-cholestanol by successive treatment with trimethylsilyl iodide and water.Pyridinium toluene-p-sulphonate has been reported as an efficient and mild catalyst for the conversion of alcohols into their tetrahydropyranyl ethers.Bile acids were efficiently performylated by treatment with 90% HCO2H-HCIO4. Selective base-catalysed... 

A review of the preparation, structures, and stereochemistry of cyclic acetals of the aldoses and aldosides has appeared. Pyridinium toluene-p-sulphonate has been reported to be a mild catalyst for the formation and cleavage of dioxolane-type acetals, although no carbohydrate examples were quoted. Acetals and ketals of carbohydrates have been used as co-agents to introduce chirality into the products of sodium borohydride reduction of acetophenone, propiophenone, etc ... 

Protection.—Pyridinium toluene-p-sulphonate has been reported as a mild and efficient acid catalyst for the formation of THP ether derivatives of alcohols and is especially useful for highly acid-sensitive cases. A new synthesis of THP ethers, which avoids acidic conditions altogether, involves the reaction of iV-(2-oxany-loxy)succinimide (43) with the magnesium derivatives of alcohols (Scheme 23). 

With excess of 2-methoxypropene and toluene-p-sulphonic acid at ambient temperature for 20 h the same two products were obtained, and in addition the diacetals (l) and (2) each in 30% yield. Compound (1) was perbenzylated, and selective hydrolysis of the eight membered ring was then effected by exposure to pyridinium toluene-p-sulphonate to give the useful diol synthon (3). 

Treatment of methyl / -maltoside with 3.7 equivalents of 2-methoxypropene in the presence of pyridinium toluene-p-sulphonate for 20 min at 0°C led to exclusive formation of acyclic acetals at the primary positions. ... 

Hydrolysis of the diethylacetal function employing p-toluenesulphonic acid in acetone, pyridinium p-toluene-sulphonate in EtOH, and a suspension of Si02 in hexane. In all cases the corresponding aldehyde is obtained in high yield as a Z E isomeric mixture. Transmetallation of acetal with Me2Cu(CN)Li2 followed by treatment with c-hexenones giving the 1,4-addition product. Alternatively, transmetallation with n-BuLi and reaction with benzaldehyde giving the expected alcohol. 

Immobilization of the required dioxolane-protected 4-Hthioacetophenone, deprotection with pyridinium p-toluene sulphonate (PPTS), and condensation with Bredereck s reagent gave resin-bound enaminone 2. The suitability of resin 2 for H-brary synthesis was verified by a trial condensation with acetamidine hydrochlori-... 

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