P-Toluenesulfonic add monohydrate

Popular conditions for the hydrolysis of dioxolane derivatives involve treatment of the substrate with either p-toluenesulfonic add monohydrate or camphorsul-fonic acid together with a small amount of water in a water-miscible solvent such as acetonitrile, THF, 1,4-dioxane, or acetone. Under these conditions secondary fert-butyldimethylsilyl ethers21 and primary ferf-butyldtphenysilyl ethers22 survive [Scheme 2,5]. If acetone is used as solvent, the deprotection can be carried out without the addition of water by a transacetalisation reaction [Scheme 2.6].23... 

Bis(hydroxymethyl) propionic acid 30.00 g (223.7 nunol), 2,2-dimethoxy-propane (41.4 mL, 335.4 mmol) and p-toluenesulfonic add monohydrate (2.10 g, 11.1 nunol) were dissolved in 100 mL of acetone. The mixture was stirred for 4 h at room temperature before 3.0 mL mixture of an ammonia solution (25 %) and EtOH (50/50, v/v)) was added into the reaction mixture to neutralize the catalyst. The solvent was removed by evaporation under reduced pressure at room temperature. The residue was then dissolved in CH2CI2 (600 mL) and extracted with two portions of water (80 mL). The organic phase was dried with anhydrous Na2S04 and evaporated to give (I) as white powder (33.0 g, 84 %). The H NMR spectra... 

METHOD 2. A mixture of 170 g of piperidine, 220 g of cyclohexylamine, and 750 ml of benzene is azeotropically distilled until the evolution of H2O stops, then vacuum distill to get cyclohexenyl-piperidine. p-toluenesulfonic acid monohydrate (190 g) in 250 ml of PhMe is heated under a water trap until all the H2O is removed, then add a solution of 165 g of cyclohexyl-piperidine in 500 ml of Et20, with cooling, to keep temp at 0°. A solution of 1 mole of PlMgBr (made from 157 g of PhBr and 24 g of Mg) in 750 ml of Et20 is added (still holding the temp at 0° to 5°). The mixture is stirred for an additional 30 min... 

A 500-ml. flask is charged with 318 g. (3 moles) of 1,2,4-tri-hydroxybutane (Note 1) and 3 g. of -toluenesulfonic add monohydrate. A few Carborundum boiling chips are added, the flask is equipped with a 30.5-cm. Vigreux column, condenser, and receiver arranged for vacuum distillation, and the contents are heated, with swirling, to dissolve the acid (Note 2). The flask is then heated in a bath held at 180-220° so that 300-306 g. of distillate, b.p. 85-87°/22 mm., is collected over a period of 2-2.5 hours (Note 3). The colorless liquid obtained is refractionated, the same apparatus being used, and two fractions are collected the first, 50-60 g., b.p. 42-44°/24 mm., wff 1.3343, is mainly water. After a negligible intermediate fraction, 215-231 g. (81-88%) of pure 3-hydroxytetrahydrofuran, b.p. 93-95°/26 mm., tin 1.4497, df1 = 1.095, is collected (Note 4). 

In the carbohydrate series, acetates can be cleaved selectively in the presence of benzoates [Scheme 4.329] and p-bromobenzoates using p-toluenesulfonic acid monohydrate (1 equivalent per acetate) in dichloromethane-methanol (9 1) at 4 C in 7 h or room temperature in 24 h. No benzoyl migration is observed. The method also works in comparable yield with camphorsulfonic add although the reaction takes 2 days at 40 and 3 days at room temperature. 

To the dry 50 mL two-necked round-bottomed flask containing the magnetic stirrer bar, add 1-methoxy-4-methylcyclohexa-1,4-diene (15.0 g, 0.121 mol) and p-toluenesulfonic acid monohydrate (0.02 g). Flush the system with nitrogen via the cone/flexible tubing adapter for 2 min and then place a stopper in the remaining neck of the flask. 

Dissolve the above syrup in dichloromethane (3 L). Add a solution of p-toluenesulfonic acid monohydrate (285 g, 1.5 mol) in tetrahydro-furan (1 L) with stirring, and after 2.5 min, quench the acid by addition of triethylamine (280 mL, 2 mol). Pour the reaction mixture into... 

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