Reaction of Quinones

Kikuchi et al. have observed that the initial attack of amine occurs at the carbonyl carbon, resulting in the formation of an ionic intermediate 26. This reaction is very sensitive to the solvent polarity. Under nitrogen atmosphere, intermediate 27 is further aminated to give 28. Oxidation of 27 and 28 gives 23 and 24, respectively. Oxidation in nitrobenzene, however, results in dealkylation products. In the presence of air and triethylamine, decomposition of aminoanthraquinones occurs. 

Alkylamination of naphthazarin copper complex (37)22 gives predominantly a mixture of 2(or 3),5-bis(alkylamino)-8-hydroxy-l,4-naphthoquinone (38) and 2,6-bis(alkylamino)-4,8-dihydroxy-l, 5-naphthoquinone 

The redox behavior of aminonaphthoquinones has been investigated by Matsuoka and co-workers.11 Reduction of quinoxaline quinone (40) by sodium dithionite in aqueous sodium hydroxide gives the corresponding leuco dye (41) which absorbs at 445nm. Compound 40 shows quinone- 

Polyhydroxybenzenes or aminophenol derivatives can be considered as leuco quinones or leuco quinoneimines. They are easily oxidized and couple 

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Reactions of quinones with radicals have been explored, and alkylation with diacyl peroxides constitutes an important synthetic tool (68). Although there are limitations, an impressive range of substituents can be introduced in good yield. Examples include alkyl chains ending with functional groups, eg, 50% yield of (70) [80632-67-3] (69,70). 

Above 160°C it is believed that additional cross-linking reactions take place involving the formation and reaction of quinone methides by condensation of the ether linkages with the phenolic hydroxyl groups (Figure 23.14). 

Reactions of quinones with enamino ketones have not been reported, but ethyl (S-anilinocrotonate (94), an enamino ester, has been shown to condense (71) with p-benzoquinone to give l-phenyl-2-methyl-3-carbethoxy-5-hydroxyindole (95). 

The high pressure Diels-Alder reactions of quinone-mono-ketals [80]... 

Diels-Alder reactions of quinones generated in situ by electrochemical oxidation in lithium perchlorate-nitromethane [105]... 

Many of the contributors to this volume have addressed the reactions of quinone methides with DNA nucleophiles. The 13C-labeled methide center has the potential of identifying the type and number of such adducts using 13C-NMR. An obvious... 

Bolton, J. L. Le Blanc, J. C. Y. Siu, K. W. M. Reaction of quinone methides with proteins analysis of myoglobin adduct formation by electrospray mass spectrometry. Biol. Mass... 

Leary, G. Miller, I. J. Thomas, W. Woolbouse, A. D. The chemistry of reactive lignin intermediates. Part 5. Rates of reactions of quinone methides with water, alcohols, and carboxylic acids. J. Chem. Soc., Perkin Trans. 1977, 2, 1737-1739. 

Gierer, J. Ljunggren, S. The reactions of lignin during sulfate pulping. Part 17. Kinetic treatment of the formation and competing reactions of quinone methide intermediates. Sven. Papperstidn. 1979, 82, 503-512. 

Soc., 110, 3318-3319. For reactions of quinones where adducts were also observed see. (b) Becker, H.-D. (1965)... 

A deuterium isotope effect is also observed in the reaction of quinones with acenaphthenes. Trost, B.M. (1967)... 

The case where the overall reaction involves several electrode reactions is even more general. An example is the reaction of quinone (Q) at a platinum electrode. This process occurs at pH <5 according to the scheme... 

The reactions of quinones with phenols and amines are endothermic due to low BDE of the formed Q—H bond. Hence, the synergism of quinones should be noticeable at elevated temperatures. The values of BDE in a few semiquinone radicals are given below ... 

Reactions of quinone with phenols and amines are endothermic however, the rate constants of reactions Q + InH are not low at elevated temperatures due to the low Ee0 values, as in the case of nitroxyl radicals reactions [4,48,49],... 

Biochemical processes, phenolic resins from, 18 769-770 Biochemical processing, 11 2 Biochemical reactions, of quinones,... 

The reactions of quinone consist essentially of various types of addition to the double bonds present in the molecule. This addition takes place ... 

To this scheme most of the reactions of quinone conform, and all those which are of most importance, e.g. the addition of HC1, HCN, amines, thiophenol, thiosulphuric acid, acid chlorides, and add anhydrides. 

As an example the reaction with aniline may be selected. In accordance with the scheme formulated, the first reaction product obtained is anilinoquinol (R=NH.C8H5). The reaction does not stop at this stage, however. Between this first reaction product and unchanged quinone still present there promptly occurs a reciprocal hydrogenation and dehydrogenation characteristic of very many of the reactions of quinone. 

Chiral boron catalysts had already been widely used in a variety of reactions before they were applied in Diels-Alder reactions220. Boron catalysts were first employed in the Diels-Alder reactions of quinones with electron-rich dienes. Kelly and coworkers221 found that stoichiometric amounts of a catalyst prepared from BH3, acetic acid and 3,3 -diphenyl-l,l/-bi-2-naphthol (344) catalyzed the reaction of 1-acetoxy-l,3-butadiene (341) with juglone (342) to afford cycloadduct 343 with 98% ee (equation 96). The reaction was supposed to proceed via a spirocyclic borate complex in which one face of the double bond of juglone was effectively shielded from attack by the diene. 

Figure 4.13 Reaction of quinone methides with wood.

Corey s retrosynthetic concept (Scheme 9) is based on two key transformations a cationic cyclization and an intramolecular Diels-Alder (IMDA) reaction. Thus, cationic cychzation of diene 50 would give a precursor 49 for epf-pseudo-pteroxazole (48), which could be converted into 49 via nitration and oxazole formation. Compound 50 would be obtained by deamination of compound 51 and subsequent Wittig chain elongation. A stereocontroUed IMDA reaction of quinone imide 52 would dehver the decaline core of 51. IMDA precursor 52 should be accessible by amide couphng of diene acid 54 and aminophenol 53 followed by oxidative generation of the quinone imide 52 [28]. 

In contrast to Nicolaou s model system, the IMDA reaction of quinone 86 to adduct 85 proceeded through an exo transition state geometry. This difference is due to the two additional substitutes attached to the diene side chain of quinone 86. A more detailed analysis (molecular modeling) of the four theoretically possible transition states (Fig. 10) reveals that an enophilic endolexo... 

Reaction of quinone 2 with l-dimethylamino-aza-l,3-pentadiene 96 in dichloromethane affords a rare example of a thiopyranoquinone 6 (Equation 40) <2000H(53)585>. 

As a final example we would like to note the reactions of quinone methide 27, which remains unchanged upon irradiation in methanol solution through a Pyrex or Vycor filter.128 Reduction is observed when 27 is irradiated in isopropyl alcohol with benzophenone or acetophenone,129 in methanol with acetophenone, or in methanol with no sensitizer through quartz.128 While the effect of ketone sensitizers is due to chemical sensitization,129 the wavelength effect is much more surprising. Further investigation showed that irradiation of methanol alone in a quartz vessel yielded ethylene glycol. The 185 nm line of the mercury arc, which is absorbed by Vycor and Pyrex, decomposes... 

Photochemical reactions of quinones with allenes have also been studied and in some cases cyclobutane formation occurs, although in competition with products derived from attack of the allene on the carbonyl oxygen. Thus, photocycloaddition of tetramethyl-l,4-benzoquinone with 1,1-dimethylallene affords the four-membered carbocycle 6 in good yield.12... 

Reductive metky/atum of quinones.2 Dimethylarenes can be obtained in high yield by reaction of quinones with methyllithium (excess) in benzene to form a dimethyl dihydrodiol, which is reduced without purification with HI in refluxing acetic acid. 

PPO catalyses the dependent oxidation of phenolics to quinones. The secondary reactions of quinones lead to the formation of polymeric brown or black pigments, which are responsible for significant post-harvest losses of fruits and vegetables [72]. Finally, induced PPO activity consists of both systemic and localized components. Systemic induction of PPO in tissues in response to all types of injuries may represent a broad, defensive role for PPO in protection of juvenile tissues from subsequent attack by a broad spectrum of pathogens and pests [71]. 

A characteristic and important reaction of quinones is reduction to the corresponding arenediols. The reduction products of 1,4-quinones are called hydroquinones ... 

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