Quinone diacetals

Semi- carbazone Oxime Hydro- quinone DIacetate of hydro-quinone Thiele acetylation product Other Derivatives... 

T. C. Tranter (36) has studied the binary copolymers based on hexamethylene diamine and -phenylene dipropionic, 3-(/>-carboxy-methyl)phenyl-butyric, 2-(/>-carbomethoxy)phenylpropionic, hydro-quinone diacetic, terephthalic, adipic, or sebacic acids. In spite of the fact that only the copolymers of hexamethylene diamine with/>-phenylene dipropionic and with 2-(/>-carbomethoxy)phenylpropionic acids show a linear softening point composition curve, Tranter claims for isomorphism in the copolymers of all the systems. In fact, their X-ray examination shows that they behave in the same basic manner, the second component dissolving in the lattice of the first until a certain critical concentration is reached, where the lattice structure changes quite abruptly to that of the second component. 

Phenols with a free ortho position can also give rise to ortfeo-quinone diacetates such as 39a and 41b, in addition to or instead of ortfeo-quinol acetates such as 41a [1, 6]. Phenols bearing a 2-methoxy group are particularly prone to regioselective Wessely oxidation to give 6-... 

The transformation of easily oxidizable substrates such as 1,4-dimethoxybenzene to the corresponding quinone diacetals occurs in high yields, as shown in equation (31). These quinone diacetals have been used as starting materials in a variety of organic syntheses. 

Quinone monoacetal, which is obtained by careful hydrolysis of quinone diacetal, can also be prepared directly y anodic oxidation under modified reaction conditions. ... 

Takacs [85] has separated the o- and p-benzoquinol acetates and o-quinone diacetate resulting from oxidation with lead tetraacetate of phenols containing an o-isopropyl, sec-butyl or tert.-butyl group. The o-derivatives were separated and purified on silica gel G. A 1 % solution of p-dimethylaminobenzaldehyde in concentrated sulphuric acid was... 

Preparation by Fries rearrangement of 2-bromo-hydro-quinone diacetate with aluminium chloride without solvent between 160° and 180° (66%) [1986], (25%) [1987]. 

A suspension of 35 g. (0.153 mole) of 2- -acetylphenylhydro-quinone in 77 ml. of acetic anhydride is treated with 0.5 ml. of concentrated sulfuric acid (sp. gr. 1.84). The hydroquinone goes into solution immediately with the evolution of much heat. The dark-colored solution is allowed to stand at room temperature overnight then it is poured into 400 ml. of water. The acetylated material is collected by suction filtration and dried. The crude 2- -acetylphenylhydroquinone diacetate is distilled at reduced pressure (b.p. 236-241°/l mm. or 182-190°/0.1 mm.), and the hot distillate is poured into 20 ml. of w-butyl alcohol (Note 11). The product immediately separates as a colorless, crystalline... 

Suspend 0.5 g of the quinone in 2.5 ml of pure acetic anhydride, and add 0.5 g of zinc powder and 0.1 g of powdered, anhydrous sodium acetate. Warm the mixture gently until the colour of the quinone has largely disappeared and then boil for 1 minute. Add 2 ml of glacial acetic acid and boil again to dissolve the product and part of the precipitated zinc acetate. Decant the hot solution from the zinc acetate and zinc, and wash the residue with 3-4 ml of hot glacial acetic acid. Combine the solutions, heat to boiling, carefully add sufficient water to hydrolyse the acetic anhydride and to produce a turbidity. Cool the mixture in ice, filter off the diacetate of the hydroquinone and recrystallise it from dilute ethanol or from light petroleum. 

The formation and intramolecular dipolar cycloaddition of azomethine ylides formed by carbenoid reaction with C=N bonds has recently been studied by the authors group.84 Treatment of 2-(diazoace-tyl)benzaldehyde O-methyl oxime (176) with rhodium(II) octanoate in the presence of dimethyl acetylenedicarboxylate or N-phenylmaleimide produced cycloadducts 178 and 179, respectively. The cycloaddition was also carried out using p-quinone as the dipolarophile. The major product isolated corresponded to cycloadduct 180. The subsequent reaction of this material with excess acetic anhydride in pyridine afforded diacetate 181 in 67% overall yield from 176. The latter compound incorporates the basic dibenzofa, d -cyclohepten-5,10-imine skeleton found in MK-801,85 which is a selective ligand for brain cyclidine (PCP) receptors that has attracted considerable attention as a potent anticonvulsive and neuro-protective agent.86,87... 

A variety of conditions have been employed to convert o-quinone dioximes into benzofurazans, including dehydration with acetic anhydride, thionyl chloride, sulfuric acid, and phenyl isocyanate, and steam distillation in the presence of alkali. Alternatively, cyclization may be achieved by boiling with aqueous alkali or thermolysis of the corresponding dioxime diacetates or dibenzoates. 

Terminal epoxides react with DMF in the presence of BiBr3 under an 02 atmosphere to afford cyclic carbonates (Equation (87)).143 Para-quinones react with acetic anhydride under the catalysis of Bi(OTf)3 to give acetoxy-1,4-hydroquinone diacetates (Equation (88)).144... 

In an example of the use of this activation method testosterone, with a IT -hydroxy group, was oxidized to A -androstene-3,17-dione very rapidly in high yield, in contrast to the use DMSO-acetic anhydride. During a reaction, when other oxidizing agents were found to be ineffective, sulfur trioxide/dimethyl sulfoxide led to smooth oxidation of the df-diol (16 equation 8) to an o-quinone in 49% yield and the ci.r-diol (17) to (18 equation 9) in 98% yield. - The use of dimethyl sulfoxide-acetic anhydride for this oxidation gave large amounts of the diacetate as the by-product. 

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