Hydroquinone derivatives, synthesis from

Source Reprinted from Shindo, H., and Huang, P. M. (1985b). The catalytic power of inorganic components in the abiotic synthesis of hydroquinone-derived humic polymers. Appl. Clay Sci. 1,71-81, with permission from Elsevier. 

Tietze, L.R and Sommer, K. (2005) Synthesis of vitamin E from (3-methyl-3-butenyl)hydroquinone derivatives. Ger. Offen. DE 102004011265. 

Monoacyl hydroquinone derivatives are, however, deacylated when treated with oxidizing agents (Ce, Tl, N-bromo-succinimide and bromine) [133, 134]. Thus the quinone (79) is prepared in high yield from the monoacetyl derivative (78) with AT-bromosuccinimide [135]. This method of deacylation is useful in the synthesis of quinones and the corresponding quinols. 

A Methylamino)phenol. This derivative, also named 4-hydroxy-/V-methy1ani1ine (19), forms needles from benzene which are slightly soluble in ethanol andinsoluble in diethyl ether. Industrial synthesis involves decarboxylation of A/-(4-hydroxyphenyl)glycine [122-87-2] at elevated temperature in such solvents as chlorobenzene—cyclohexanone (184,185). It also can be prepared by the methylation of 4-aminophenol, or from methylamiae [74-89-5] by heating with 4-chlorophenol [106-48-9] and copper sulfate at 135°C in aqueous solution, or with hydroquinone [123-31 -9] 2l. 200—250°C in alcohoHc solution (186). 

Ishikawa and coworkers reported a synthesis of ( )-0-methylkinamycin C (54) [32, 33]. Their retrosynthetic analysis is shown in Scheme 3.9. It was envisioned that 54 could be derived from the dihydroindanone 55 by D-ring oxygenation, installation of the diazo substituent, and oxidation of the protected hydroquinone function. The dihydroindanone 55 was envisioned to arise from the enol ether 56, itself formed from an endo Diels-Alder reaction between the indenone 59 and the diene 58. 

Sunlight irradiation (solar photochemical synthesis) of 1,4-naphthoquinone (27) in the presence of aldehyde (28) in a mixture of -butanol and acetone gives a good yield of the corresponding acyl hydroquinone (29) through the abstraction of the formyl hydrogen atom of aldehyde by the excited triplet biradical derived from 1,4-naphthoquinone, followed by the reaction of the acyl radical with 1,4-naphthoquinone (eq. 12.7). Here,... 

Derivatives of phenol or aniline can be oxidized to quinones, the yield and ease of oxidation depending on the substituents. If an amino or hydroxyl group is in the para position, the reaction proceeds readily, as illustrated by the synthesis of quinone from hydroquinone by oxidation with a sodium chlorate-vanadium pentoxide mixture (5>6%) or with chromic-sulfuric acid mixture (92%). A para halogen atom usually has a favorable effect. Any group in the para position is eliminated or oxidized. o-Quinones are usually prepared from the corresponding catechols. A survey of procedures for the synthesis of benzoquinones by oxidation has been made. ... 

A systematic study of numerous homo PEIs derived from 27b and various diphenols was conducted by the author [21,52,53]. This study revealed that the dicarboxylic acid has good mesogenic properties despite its lack of symmetry, and some unexpected structure property relationships were detected. The PEIs of unsubstituted hydroquinone was not prepared, because a Tm above 450 °C was expected. Even the smallest substituent (e.g. Cl or CH3) reduces the Tm to values below 400 °C (33a, c, see Table 4). In fact the PEIs of all monosubstituted hydroquinones (33a-i) were thermotropic with broad nematic phases. Remarkable is the reluctance to crystallize in the case of 33g. Three days of annealing were required to obtain a crystallinity below 20%. Also other more or less bulky substitutes, such as those of 33d, h and i reduce the tendency to crystallize. As discussed below, (and in Sect. 4), this is an interesting aspect for the synthesis of... 

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... 

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