Thiele reactions, acetic anhydride

Thiele reaction Acetic anhydride. Acetic phosphoric anhydride. Boron trifluoride etherate. 

Finally, Thiele acetoxylation of quinones, by treatment with acetic anhydride and sulfuric acid, is another excellent method of introducing functionality at an alkene carbon atom, for further synthetic elaboration (equation 50)196. This reaction was recently used as a key synthetic step in the total synthesis of metachromin-A, a useful sesquiterpene quinone moiety197. 

The behaviour of p-benzoquinone on reaction with acetic anhydride in the presence of sulphuric acid is of interest. The eventual product is 1,2,4-triacetoxybenzene (the Thiele acetylation), which is formed by the following... 

Thiele and Schleussner prepared ira/ii,franj-l,4-diphenylbutadiene by reaction of cinnamaldehyde with sodium phenylacetate and acetic anhydride at a temperature such that the initially formed product of Perkin condensation loses carbon dioxide. Kuhn and Winterstein employed lead oxide as the base and reported an increase in crude yield from 20 to 34%. The lower yield of 23-25% reported in Organic... 

Thiele reaction. Formation of triacetoxy aromatic compounds by the reaction of quinones with acetic anhydride catalyzed by sulfuric acid or boron trifluoride. 

The reagent can be used also for the Thiele reaction, that is, acid-catalyzed addition of acetic anhydride to a quinone with further conversion into the hydroquinone... 

Thiele reaction. In a typical Thiele reaction,45 1,4-benzoquinone (1) is added with stirring at room temperature or below to a solution of a catalyst such as concentrated sulfuric acid in acetic anhydride 1,4-addition to (2) is followed rapidly by enolization (3) and acetylation to give 1,2,4-triacetoxybenzene (4) in high yield. In a few cases Thiele used zinc chloride as catalyst but without apparent advantage. Boron trifluoride etherate would appear to be a more satisfactory Lewis acid since... 

Discovery of the dienone-phenol rearrangement of quinol acetates has made possible the synthesis of dihydric phenols that were difficult of access by other routes. The starting materials are obtained from phenols and lead tetraacetate, and with acetic anhydride and sulfuric acid (Thiele acetylation) or with boron trifluoride in ether they give, respectively, di- and mono-acetyl derivatives of resorcinol or hydroquinone.309 When treated with lN-sodium hydroxide, 0-quinol acetates of type (1) undergo nucleophilic addition of an OH" ion, giving resorcinol derivatives (2).310 Occurrence of the reaction is considered... 

The synthetic scope of the Thiele-Winter reaction of quinines with acetic anhydride can be increased by the use of triflic acid (eq 46). Reaction of cyclopropylacylsilanes with triflic acid in aprotic solvent affords the corresponding cyclobutanone or 2-silyl-4,5-dihydrofuran derivatives. Triflic acid can react with >-iodosylbenzoic acid to form a hypervalent iodine reagent, which reacts with 1-trimethylsilylalkynes to afford alkynyliodonium tri-flates bearing a carboxy group in high yields (eq 47). Reaction of (diacetoxyiodo)benzene [PhI(OAc)2] with excess triflic acid results in oligomerization of PhI(OAc)2- ... 

Thiele Reaction. The Thiele reaction converts 1,4-benzoquinone to 1,2,4-triacetoxybenzene using acetic anhydride and a catal34ic amount of sulfuric acid. Zinc chloride has been used without advantage. In this reaction, 1,4-addition to the quinone is followed by enolization and acetylation to give the substituted benzene (eq 41). 

With unhindered quinones, BF3 etherate is a more satisfactory catalyst hut hindered quinones require the more active sulfuric acid catalyst. 1,2-Naphthoquinones undergo the Thiele reaction with acetic anhydride and sulfuric acid or horon trifluoride etherate (eq42). 

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