Acetyl p-toluenesulfonate

Furan can also be acylated by the Vilsmeier-Haack method. Acylation of furans can also be carried out with acid anhydrides and acyl halides in the presence of Friedel-Crafts catalysts (BF3-Et20, SnCU or H3PO4). Reactive anhydrides such as trifluoroacetic anhydride, however, require no catalyst. Acetylation with acetyl p-toluenesulfonate gives high yields. 

Acetyl p-toluenesulfonate [26908-82-7] M 214.2, m 54-56°. The most likely impurity is p-toluenesulfonic acid (could be up to 10%). This can be removed by dissolving in dry Et20 and cooling until the anhydride crystallises out. It decomp on heating below -130° it gives the disulfonic anhydride and above -130° polymers are formed. It is used for cleaving ethers [Prep, IR, NMR Karger and Mazur J Org Chem 36 528, 532 1971]. 

Ethers Acetyl p-toluenesulfonate. Boron tribromide. Boron trichloride. Boron trifluoride etherate—Acetic anhydride. Ferric chloride. Methylmagnesium iodide. Pyridine hydrochloride. Sodium borohydride. Sodium iodide. 

Cyclization. The dione (1) is converted into the estrane (2) by acetyl p-toluenesulfonate in acetic anhydride. Cychzation of (1) by the usual reagents is accompanied by dehydration. Thus cychzation of (3), which lacks a Ci i-keto group, gives (4). 

Acylation with anhydrides, catalysed by phosphoric acid, is an efficient method reaction with acetyl p-toluenesulfonate, in the absence of any catalyst, produces 2-acetylthiophene in high yield. " Vilsmeier formylation leads efficiently to 2-formylthiophene. ... 

The specific rates of solvolysis of the acid anhydride, acetyl p-toluenesulfonate (30) were measured by a rapid-response conductivity technique at temperatures in the range 263-218 K. For 13 solvents at 233.4 K, an extended Grunwald-Winstein equation correlation led to sensitivities to changes in solvent nucleophilicity of 0.65 and to changes in solvent ionizing power of 0.61. In 89.1 % acetone at 253 K, the comparison with acetyl bromide solvolysis led to a koj /k ratio of 1.4. In methanol and methanol-d at 233.4 K, the solvent deuterium isotope effect A MeOH MeOD was 0.99. These results are consistent with an 5 1 reaction with appreciable nucleophilic solvation or an 5 2 reaction with a loose TS. ... 

AcCl also reacts with anhydrous p-toluenesulfonic acid (3-4 equiv AcCl, A) to afford acetyl p-toluenesulfonate in 97.5% yield along with anhydrous HCl. AcCl does not react with HOAc to generate HCl and AC2O, at least in appreciable amounts. ... 

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