1,4-Naphthoquinone reduction

Reduction, (a) By sulphurous acid. Benzoquinone, /> toluquinone, 1,2-naphthoquinone are readily reduced by SOj ultimately to the dihydroxy-compound. Thus benzoquinone gives colourless hydro-quinone or quinol, />-C2H4fOH)2. 

Naphthalenediol. This diol can be prepared by the chemical or catalytic reduction of 1,4-naphthoquinone. Both the diol and quinone are of interest because of their relation to the vitamin K family. Carboxylation of 1,4-naphthalenediol with CO2—K2CO2 followed by neutralization gives... 

The synthetic procedure described is based on that reported earlier for the synthesis on a smaller scale of anthracene, benz[a]anthracene, chrysene, dibenz[a,c]anthracene, and phenanthrene in excellent yields from the corresponding quinones. Although reduction of quinones with HI and phosphorus was described in the older literature, relatively drastic conditions were employed and mixtures of polyhydrogenated derivatives were the principal products. The relatively milder experimental procedure employed herein appears generally applicable to the reduction of both ortho- and para-quinones directly to the fully aromatic polycyclic arenes. The method is apparently inapplicable to quinones having an olefinic bond, such as o-naphthoquinone, since an analogous reaction of the latter provides a product of undetermined structure (unpublished result). As shown previously, phenols and hydro-quinones, implicated as intermediates in the reduction of quinones by HI, can also be smoothly deoxygenated to fully aromatic polycyclic arenes under conditions similar to those described herein. 

In addition to the oxidation-reduction potentials data, two sets of infrared carbonyl stretching frequencies were correlated with eqs. (2) and (30). Of these, one set, Pqq for 2-substituted 1,4-naphthoquinones, gave significant results, with Pr of about 50. While the other set did not give significant correlation, it contained only four points. Although the sharp difference between pr for vqq and pR for Ep correlations of 2-substituted 1,4-naphthoquinones is worthy of note, it should not be discussed until it is confirmed by further work. 

Reduction of monocyclic aromatic nitro compounds has been demonstrated (a) with reduced sulfur compounds mediated by a naphthoquinone or an iron porphyrin (Schwarzenbach et al. 1990), and (b) by Fe(II) and magnetite produced by the action of the anaerobic bacterium Geobacter metallireducens (Heijman et al. 1993). Quinone-mediated reduction of monocyclic aromatic nitro compounds by the supernatant monocyclic aromatic nitro compounds has been noted (Glaus et al. 1992), and these reactions may be signihcant in determining the fate of aromatic nitro compounds in reducing environments (Dunnivant et al. 1992). 

In the case of the naphthoquinone methine-type near-IR dye 55, reduction with tin(II) chloride under acidic conditions gives the leuco dye 56, which has weak absorption maxima at 350-359nm in methanol. The leuco dye 56 can be isolated as a stable pale yellow compound. The oxidation behavior of 56 has been studied by adding benzoquinone as oxidant in methanol solution. Compound 56 immediately produced new absorption at 760 nm which is consistent with the absorption maximum of 55 (Scheme 19).30 The absorption spectra of the leuco, quinone, and metal complex forms are summarized in Table 3. 

Typically, the synthesis of block B involves the Diels-Alder reaction of 1,4-naphthoquinone with cyclopentadiene, followed by reduction and OH methylation to give 92 (Scheme 33). The next step involves a Ru-catalysed [2+2] cycloaddition of 92 with dimethyl acetylenedicarboxylate (DMAD), followed by epoxidation (MeLi, BuOOH) to give 94 as block B. 

Naphthoquinone is reduced to 1,2,3,4-tetrahydronaphthalene with Et3SiH/TFA in 60% yield.393 Quinones can be reduced to hydroquinones in good yields with hydridosiloxanes such as TMDO with iodide present (Eq. 209).314,316,357 The reductive dehydration of a 1,3-diketone leads to an enone (Eq. 210).374... 

Naphthoquinone, ketone-alcohol reduction, diastereoselectivity, 76-77 Nitrile reduction, a,/3-unsaturated nitriles, 96... 

Other Quinones.—Look up o-quinones and the three naphthoquinones the best method of preparing a- and / -naphthoquinone is froml 4-andl 2-aminonaphthol respectively, which are obtained from azo-dyes of the two naphthols by reduction (see p. 302). 

Brimble and coworkers176 studied the asymmetric Diels-Alder reactions of cyclopentadiene with chiral naphthoquinones 272 bearing different chiral auxiliaries. The highest endo and facial selectivities were obtained using zinc dichloride as the Lewis acid catalyst and (—)-pantolactone as the chiral auxiliary. Thus, the reaction between cyclopentadiene and 272 afforded a 98 2 mixture of 273 and 274 (equation 76). The chiral auxiliary was removed easily by lithium borohydride reduction. 

Buffinton, G.D., Olhnger, K., Brunmark, A., and Cadenas, E., 1989, DT-diaphorase catalyzed reduction of 1,4-naphthoquinone derivatives and glutathione-conjugates. Biochem. J. 257 561-571... 

Fig. 3 Electrochemical and homogeneous standard free energies of activation for self-exchange in the reduction of aromatic hydrocarbons in iV.A -dimethylformamide as a function of their equivalent hard sphere radius, a. 1, Benzonitrile 2, 4-cyanopyridine 3, o-toluonitrile 4, w-toluonitrile 5, p-toluonitrile 6, phthalonitrile 7, terephthalonitrile 8, nitrobenzene 9, w-dinitrobenzene 10, p-dinitrobenzene 11, w-nitrobenzonitrile 12, dibenzofuran 13, dibenzothiophene 14, p-naphthoquinone 15, anthracene 16, perylene 17, naphthalene 18, tra 5-stilbene. Solid lines denote theoretical predictions. (Adapted from Kojima and Bard, 1975.)...

Lithium aluminum hydride reduced p-benzoquinone to hydroquinone (yield 70%) [576] and anthraquinone to anthrahydroquinone in 95% yield [576]. Tin reduced p-benzoquinone to hydroquinone in 88% yield [174] Procedure 35, p. 214). Stannous chloride converted tetrahydroxy-p-benzoquinone to hexa-hydroxybenzene in 70-77% yield [929], and 1,4-naphthoquinone to 1,4-di-hydroxynaphthalene in 96% yield [180]. Other reagents suitable for reduction of quinones are titanium trichloride [930], chromous chloride [187], hydrogen sulfide [248], sulfur dioxide [250] and others. Yields are usually good to excellent. Some of the reagents reduce the quinones selectively in the presence of other reducible functions. Thus hydrogen sulfide converted 2,7-dinitro-phenanthrene quinone to 9,10-dihydroxy-2,7-dinitrophenanthrene in 90% yield [248]. 

Further reduction of quinones - acquisition of four or more hydrogens per molecule - was achieved with lithium aluminum hydride which reduced, in yields lower than 10%, 2-methyl-1,4-naphthoquinone to 1,2,3,4-tetrahydro-l,4-dihydroxy-2-methylnaphthalene and to l,2,3,4-tetrahydro-4-hydroxy-l-keto-2-methylnaphthalene [931]. Lithium aluminum hydride [931], sodium borohydride, lithium trie thy Iborohydride and 9-borabicyclo[3.3.1Jnomine [100] converted anthraquinone to 9,10-dihydro-9,10-dihydroxyanthracene in respective yields of 67, 65, 77 and 79%. 

The half-wave reduction potentials for a series of annelated 1,4 naphthoquinones (102-106) increase upon alkylation, and decrease as ring size decreases (Table 13). The more cathodic reduction potentials of 2,3-dimethylnaphtho-l,4-qui-none (106, 0.846 V) and l,2,3,4-tetrahydro-9,10-anthroquinone (105,0.854 V) as compared to 1,4-naphthoquinone (0.685 V) are expected from inductive electron donation of alkyl groups. A decrease in reduction potential from 105 to 2,3-cyclobutanaphtho-l,4-quinone (103) (0.695 V) as ring size decreases is observed such that the reduction potential of 103 is only slightly higher than the parent 1,4-naphthoquinone. 

Another example is provided by the polarographic reduction of 1,2-and 1,4-naphthoquinones (R) in various solvents in the presence of metal ions (21) ... 

Fig. 2. E1/2 values for the reduction of 1,2-naphthoquinone in the presence of different metal ions plotted against donicity of solvent...

The phytochemical reducibility of quinones was first demonstrated in the case of p-xyloquinone. This compound is worthy of interest since it is very easily formed from diacetyl by purely chemical means through a type of aldol condensation followed by ring closure. It is reduced to p-xylohydroquinone by fermenting yeast. Benzoquinone, thymoquinone and a-naphthoquinone similarly yield the corresponding hydroquinones. Tetrabromo-o-quinone and anthraquinone proved resistant to attack, while phenanthraquinone could be reduced phyto-chemically to phenanthrahydroquinone in poor yield (9%). Phytochemical reduction can also be accomplished in the dicyclic terpene series. According to unpublished experiments by Neuberg and Peiser, 2,3-dihy-... 

Another redox switchable system is based on dyad 21 in which 2-chloro-1,4-naphthoquinone is covalently attached to 5-dimethyl-aminonaphthalene via a non-conjugated spacer. The intrinsic fluorescence of the dansyl excited state in dyad 21 is strongly quenched, due to the intramolecular electron transfer from the excited dansyl to the adjacent quinone acceptor. However, the fluorescence can be switched on by addition of a reducing agent. Apart from chemical switching, the fluorescence of dyad 21 can also be switched electrochemically. This can be realized using a photoelec -trochemical cell, and the solution starts to fluoresce upon application of a reductive potential.31... 

Another interesting feature is the synthesis of benzo- and naphthoquinones succeeding via the reductive elimination from metallacycloheptadienediones. The latter are formed by an alkyne insertion into metallacyclopentenediones.8... 

Fig. 8.16 Influence of metal ions on the DC polarographic reduction wave of 1,2-naphthoquinone (0.5 mM) in AN-0.05 M Et4NCl04 [60 b]. Metal ions (5 mM) curve 1, none 2, l<+ ...

Fig. 8.17 Relationship between the half-wave potential and the standard rate constant for the first reduction wave of various organic compounds in AN. The influence of R4N+ of the supporting electrolyte [61 a). Compounds 1, hexafluorobiacetyl 2, p-benzoquinone 3, 1,4-naphthoquinone 5, oxygen 6, 9,10-anthra-quinone 8, p-nitrotoluene 9, 4,4 -methoxyben-zyl 10, 2,3-butanedione 11, nitromesitylene ...

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