Synthesis of Quinones

4-hydroquinone Ig and the hydroquinone monomethyl ether Ih were converted into the para-quinones 3a and 3e in high yields (Fig. 4). 

The rich topic of the utilization of ortho- and para-quinones in chemical synthesis falls outside the scope of this review, but there is a quite elegant and 

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The general applicability of this type of synthesis of quinone diazides is nevertheless limited since, depending on the type and number of substituents in the 2-, 4-, and 6-positions of benzenediazonium ions, either hydroxy-de-diazoniation (reaction A in Scheme 2-20) or nucleophilic substitution of one of the groups in the 2-, 4-, or 6-position (reaction B) will predominate. It is difficult to predict the ratio of the two reactions in a specific case. This is exemplified by two investigations carried... 

Tremendous effects have been made in studying the possibilities for the electrochemical generation and regeneration of inorganic redox agents like Cr(VI) V(V), Mn(III) Ce(IV) , and Co(in) and their application in the oxidation of aromatics. These studies are mainly performed by means of three types of reactions side-chain oxidations to form benzaldehydes, side-chain oxidations to generate benzoic acids, and nuclear oxidations for the synthesis of quinones (Scheme 1). 

E. Muller, Quinone Symp., Univer.sity of Aberdeen, 1971, Abstr. Pap. (Synthesis of quinones using transition metal complexes). 

The sulfur compound sulfuraphane, extracted from fresh broccoli, has received attention in recent years because of its strong action in inducing synthesis of quinone reductase and glutathione S-transferases that help detoxify xenobiotics and may have significant anticancer activity/... 

With benzene the product is o-benzoylbenzoic acid (Expt 6.124), and with toluene, o-(p-toluoyl)benzoic acid (Expt 6.132). The aroylbenzoic acids are important starting materials for the synthesis of quinones (Section 6.11.3, p. 1022), into which they are cyclised using polyphosphoric acid (Expt 6.132). 

Use of transition metal catalysts opens up previously unavailable mechanistic pathways. With hydrogen peroxide and catalytic amounts of methyl trioxorhe-nium (MTO), 2-methylnaphthalene can be converted to 2-methylnaphtha-l,4-qui-none (vitamin K3 or menadione) in 58 % yield and 86 % selectivity at 81 % conversion (Eq. 10) [43, 44]. Metalloporphyrin-catalyzed oxidation of 2-methylnaphtha-lene with KHSOs can also be used to prepare vitamin K3 [45]. The MTO-catalyzed process can also be applied to the synthesis of quinones from phenols [46, 47]. In particular, several benzoquinones of cardanol derivatives were prepared in this manner [48], The oxidation is thought to proceed through the formation of arene oxide intermediates [47]. 

An interesting report on the synthesis of quinone imines was the oxidative cyclization of phenylalkylazides with phenyliodine(m) bis(trifluoroacetate) (PIFA) (Equation 20) <1999CPB241>. 

Synthesis of quinone derivatives containing saturated O-heterocyclic substituents as 5-lipoxygenase inhibitors and antagonists of thromboxane A2 receptors 92YGK786. 

During a synthesis of quinone imine precursors to the Dynemicins, Myers and co-workers100 encountered problems with the lability of the dimethyl acetal function in 56,1 [Scheme 1.56] whilst removing the robust phenolic methyl group using sodium ethanethiolate in hot DMF, However prior conversion of the free hydroxy function in the substrate to the magnesium salt 56.2 by reaction with ethylmagnesium bromide afforded protection for the dimethylacetal under the strenuous conditions of nucleophilic demethylation. 

The synthesis of quinones, including anthracyclinone antibiotics and oxidized metabolites of polynuclear aromatic hyditxarbons, has been reviewed. 

The synthesis of quinones from arenes is an area which demands further research, despite the number of reagents presently available for this transformation. This is highlighted by the synthesis of the naphthoquinone (3). Direct oxidation of the dibromoarene (1) was unsatisfactory, and therefore Bruce and coworkers had to resort to a multistep sequence involving nitration, reduction, diazotization, displacement by hydroxide and finally oxidation of the phenol (2) with Fremy s salt (Scheme 1). Although there are examples of the oxidation of polynuclear aromatic hydrocarbons to quinones, the direct oxidation of an arene to a quinone is a process not encountered in the synthesis of more complex mt ecules. 

Fremy s salt (potassium nitrodisulfonate) is a widely used reagent, particularly in the synthesis of quinone antibiotics. One example has emerged from Kozikowski s group in their approach to the rubra-dirin antibiotics. The MEM-protected 2-nitroresorcinol (4) was converted in several steps to the phenol... 

Cerium(IV) ammonium nitrate has been used increasingly during the last decade in the synthesis of quinones, particularly as a means of effecting oxidative demethylation of methoxyarenes. 

Lead tetraacetate is a versatile reagent which has many applications in organic synthesis, not least in the synthesis of quinones. ... 

There are numerous other examples of the synthesis of quinones employing reagents such as nitric acid, manganese dioxide, salcomine/02, silver oxide, " chromium oxidants, >2 -47... 

Bilgic, O. and Young, D. W., A general and practicable synthesis of polycyclic hctcroar-omatic compounds. III. Extension of the synthesis of quinone-methidcs of naphthalene, phenanthrene, and benzene, J. Chem. Soc. Perkin Tram. I. 1233, 1980. 

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