In 1898, Johannes Thiele described the reaction of p‐benzoquinone with acetic acid in the presence of a small quantity of sulfuric acid to give 1,2,4‐triacetoxybenzene in 80% yield. Later Thiele and Winter described further experiments that showed both 1,2‐ and 1,4‐naphthoquinone gave 1,2,4‐triacetoxynaphthalene and that the same product was obtained when sulfuric acid was replaced by zinc chloride. Thiele‐Winter acetoxylation can be defined as the acid‐catalyzed reactions of quinones with acetic acid to give triacetoxy aromatic compounds. This reaction has been carried out on a large number of quinones and to this point there has been no review. Very little work has been done on the reaction of quinones with anhydrides other than acetic anhydride. Results of these studies are summarized. Reactions with other anhydrides are discussed.

Thiele acetylation of all mono-, di-, and tri-bromo-p-benzoquinones, and of iodo-and 2.6-di-iodo-p-benzoquinone is described. Contrary to a previous report, 2.6-dichloro-p-benzoquinone readily undergoes Thiele acetylation. The assignments of orientation of some previously reported dibromotrimethoxy-benzenes have been shown to be erroneous.

2-Hydroxybiphenylene has been prepared by Baeyer-Villiger oxidation of the corresponding 2-benzoyl compound, itself made by direct substitution in biphenylene. The hydroxy-compound couples with diazonium salts in position 3, as predicted by Longuet-Higgins. Oxidation of the hydroxycompound with potassium nitrosodisulphonate gives biphenylene-2,3quinone (V) which is more conveniently prepared through the azophenol (III). This quinone, the first to be prepared in the biphenylene series, is remarkably stable. Under the conditions of Thiele acetylation, it behaves anomalously and yields a tetra-acetate (VI).STUDIES of hydroxybiphenylenes and biphenylenequinones have been hampered by the inaccessibility of the hydroxy-compounds. Reaction of biphenylene with lead tetraacetate followed by hydrolysis gives 2-hydroxybiphenylene in 1.5% yield; the same compound can be made by acid hydrolysis of its methyl ether, but the latter also is difficultly ac~essible.~ 2-Acetylbiphenylene did not undergo the Baeyer-Villiger reaction and attempts to cleave the ether groups of 2,7-dimethoxybiphenylene have been unsuccessful.* We have now found that 2-benzoylbiphenylene is readily converted into 2-benzoyloxy-and thence into 2-hydroxy-biphenylene. Some reactions of this compound, including its conversion into biphenylene-2,3-quinone, are described below.Biphenylene (I; R = H) reacted with benzoyl chloride in the presence of aluminium chloride to give 2-benzoylbiphenylene (I; R = Bz), the orientation of which was proved by conversion of the corresponding oxime into 2-benzamidobiphenylene (I; R = NHBz) by a Beckmann rearrangement. When the ketone (I; R = Bz) was treated with peracetic acid in acetic acid containing sulphuric acid (conditions critical), it gave the benzoate (I; R = OBz) which on alkaline hydrolysis yielded 2-hydroxybiphenylene (11) in ca. 23% overall yield from biphenylene.The phenol (11) coupled readily with diazonium salts to give deep red azo-compounds

The three monobromo-monornethoxy-p-benzoquinones have been prepared ; they all undergo Thiele acetylation.The entering acetoxy-group is found orrho or para to the bromine atom in each of the triacetates. and never ortho to the methoxy-group.Thiele acetylation of the three isomeric dibromo-rnonomethoxy-p-benzoquinones and the three monobrornodirnethoxy-p-benzoquinones has been studied. Of these six compounds the only two which undergo the reaction are 2.6-dibrorno-3-rnethoxyand 2-bromo-5.6-dimethoxy-p-benzoquinone.

Baeyer-Villiger oxidation of 2-acetylbiphenylene and its 6-benzoyl and 3-methoxy-derivatives gave the corresponding 2-acetoxy-compounds. Similar oxidation of 2,6-diacetylbiphenylene gave a mixture of 2-acetoxy-6-acetyl-and 2,6-diacetoxy-biphenylene. These compounds were converted into 2-acetyl-6-methoxy-and 2.6-dimethoxy-biphenylene, respectively, by combined hydrolysis and methylation. Oxidation of 2,7-diacetylbiphenylene gave the 2.7-diacetoxy-compound.Fries rearrangement of 2-acetoxybiphenylene gave the 2-acetyl-3-hydroxy-compound, which was methylated to 2-acetyl-3-methoxybiphenylene. The latter was also obtained by Friedel-Crafts acetylation of 2-methoxybiphenylene.RECENTLY it was reported2 that 2-benzoyl-but not 2-acetyl-biphenylene could be oxidised by peracetic acid in acetic acid (Baeyer-Villiger reaction3) to give the corresponding ester of 2-hydroxybiphenylene. This oxidation required a relatively large amount of concentrated sulphuric acid as catalyst. It has now been found that 2-acetyl-can be oxidised to 2-acetoxybiphenylene in 84% yield in the absence of added sulphuric acid provided that stronger peracetic acid is used (commercial peracetic acid often contains traces of sulphuric acid which must be removed, otherwise the yield is decreased to 61%).2-Acetyl-6-benzoylbiphenylene (I ; R = PhCO) (m. p.175") has been made by acetylation of 2-benzoylbiphenylene and, in lower yield, by benzoylation of 2-acetylbiphenylene. When it was treated with peracetic acid the more reactive carbonyl group, i.e., the acetyl group, underwent preferential oxidation to give a mixture of 2-acetoxy-6-benzoyl-and 2-acetoxy-6benzoyloxy-biphenylene, which was very difficult to separate. These two products, on combined hydrolysis and methylation, gave 2-benzoyl-6-methoxy-and 2,6-dimethoxy-biphenylene, respectively. The formation of the latter confirmed the orientation assigned to 2-acetyl-6-benzoylbiphenylene.2,6-Diacetylbiphenylene (I ; R = CH,CO) (m. p. 254.) is sparingly soluble in peracetic acid, but it reacted slowly to give a mixture of 2,6-diacetoxy-and a little 2-acetoxy-6-acetyl-biphenylene. These compounds were converted into 2,6-dime thoxybiphenylene and 2-acetyl-6-methoxybiphenylene ( I ; R = MeO), respectively, by hydrolysis and methylation. 2,7-Diacetylbiphenylene (m. p. 174") is moderately soluble in acetic acid and oxidation with peracetic acid readily occurred, though the yield of 2,7-diacetoxybiphenylene was rather low (23%).2-Acetoxy-biphenylene readily underwent Fries migration to give 2-acetyl-3-hydroxybiphenylene , which on