Thiele-Winter acetoxylation

What is Thiele-Winter acetoxylation?

In 1898, Thiele reported a reaction that was later extended by Thiele and Winter in 1900. Thiele-Winter acetoxylation involves the addition of acetic anhydride Ac2O (see list of acronyms) to quinones under the influence of strong acid catalysts to yield triacetoxy aromatic derivatives. Thiele-Winter acetoxylation is commonly known as the Thiele acetoxylation, Thiele acetylation, Thiele-Winter reaction, Thiele reaction, or Thiele addition. Occasionally, the analogous transformation of a quinoid to 2,4-diacetoxy toluene is referred to as the Thiele rearrangement.

Thiele-Winter acetoxylation - general reaction scheme - Thiele acetoxylation - Thiele acetylation - Thiele-Winter reaction - Thiele reaction - Thiele addition - Thiele rearrangement
Thiele-Winter acetoxylation

While H2SO4 and boron trifluoride BF3 etherate are common catalysts for this reaction, CF3SO3H and HClO3 have also been found to be effective. The potency of the catalysts depends on the type of quinone being used. H2SO4 is especially effective for the benzoquinone series, whereas BF3 is superior for the α-naphthoquinone series.

However, some quinones, such as 2,5-dimethoxy-1,4-quinone, 2,6-dimethoxy-1,4-quinone, 2,3,5-trimethyl-1,4-quinone, 2,6-dichloro-1,4-quinone, and 2-alkyl-1,4-naphthoquinone, do not undergo Thiele-Winter acetoxylation. It has also been observed that 2,5-dialkyl quinones are more reactive than 2,6-isomers, and the acetoxylation of di-t-butylbenzoquinone may result in the elimination of one of the t-butyl groups.