Quinones from polycyclic aromatics

Peter H. Given. One of the important questions we have to solve in coalification is how polycyclic aromatic substances come to be formed. Was the benzotropolone positively identified This is an interesting way in which polycyclic compounds are formed from monocyclic. Is it your idea that quinone adducts are formed in the biochemical decay and that these adducts are transformed into polycyclic aromatics by the action of heat after burial ... 

Quinones of the more reactive, polycyclic, aromatic systems can usually be obtained by direct oxidation, which is best carried out with chromium(vi) compounds under acidic conditions. In this way 1,4-naphthoquinone, 9,10-anthraquinone and 9,10-phenanthraquinone are prepared from naphthalene, anthracene and phenanthrene respectively (Expt 6.128). Also included in this section is the reduction of anthraquinone with tin and acid to give anthrone, probably by the sequence of steps formulated below. 

Aromatic compounds may be oxidized either through epoxidation or via addition of oxygen atom from Cpd I (Scheme Id). Usually, both pathways afford more stable phenols or quinones as the end product through rearrangements and/or addition of another nucleophile. Direct abstraction of an electron from aromatic moiety is viable in the presence of strong electron-donating substituents. The oxidative metabohsm of polycyclic aromatic compounds is represented by CYPlAl in humans. 

AhR-mediated activity results Dioxin-like activity is a useful marker of compounds that are able to activate the AhR receptor, which had been shown to be involved in numerous health effects such as impairment of immunity and nervous system or reproduction (Mukeijee 1998). There have been several studies describing AhR-mediated effects of the PMi (Wenger et al. 2009) and PMio (Clemons et al. 1998 Ciganek et al. 2004 Brown et al. 2005) aerosol size fractions. The TEQ calculated from the data of 28 PAHs (25 parent PAHs, retene, biphenyl and triphenylene) represents by average 7.5 and 95% of the dioxin-like activity associated with the particulate and gaseous fractions, respectively. Most of the activity could be produced by dioxins and furans, but also by partly oxygenated PAHs, such as polycyclic aromatic ketones and quinones that were also shown to activate AhR and to be produced by combustion pollution sources (Misaki et al. 2007). The results, furthermore, confirm that a significant portion of the AhR-mediated activity was produced by compounds present in the gas-phase at many polluted localities as it have been shown previously (Klein et al. 2006 Novak et al. 2009). 

Polycyclic organic matter, derived from the total exhaust emission, is an extremely complex mixture. It includes a large number of compounds such as polynuclear aromatic hydrocarbons (PAH), derivations of PAH such as nitro-PAH and amino-PAH, oxygenated PAH such as phenols and quinones, and heterocyclic aromatic compounds containing sulfur and oxygen. In order to assist in the identification of classes of toxic compounds it is possible to fractionate the exhaust emissions into vapor and... 

The V-Mo-O oxides are well-known industrial catalysts for the synthesis of acrylic acid from acrolein and maleic anhydride from benzene more recently, V-P-0 systems are being utilized for maleic anhydride production from -butane. The V20s/Ti02 combination was employed for phthalic acid production from o-xylene. V-Fe-O catalyzes oxidation of polycyclic aromatic hydrocarbons to dicarboxylic acids and quinones. Methyl formate is produced by the oxidation of methanol over V-Ti-0 catalysts [58]. For many of these processes, it has been experimentally proved that the catalytic reaction follows a Mars-van Krevelen mechanism. The surface coverage with active oxygen 0 in the steady state of the redox reaction following Mars-van Krevelen mechanism is given by... 

The zinc chloride-catalyzed condensation of polycyclic aromatic hydrocarbons with pyromellitic dianhydride at temperatures of 250°-300°C yielded dark, insoluble, infusible polymers. Their structure was not unequivocally determined. Judging from what is known in the literature, they could possess either a quinone [39] or a lactone [40] type structure, with the former predominating (22, 30). 

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. 

The Dess-Martin periodinane 8 is also able to oxidize aromatic compounds to the corresponding quinones. The presence of water is important and, starting from anilides 42 substituted in the 2-position, the rare class of ortho-imido-quinones 43 is accessible, Scheme 21. It has been shown that compounds of type 43 are interesting building blocks and can lead to polycyclic molecules of diverse molecular architecture [95,96]. They can undergo subsequent Diels-Alder reactions and intramolecular versions have been used for a rapid access to natural products and for synthesis of scaffolds for further manipulation.para-Quinones 45 are also easily accessible, however, only in modest yields by reacting 4-sub-stituted anilines 44 under the same reaction conditions, Scheme 21 [97]. 

An elegant new synthesis of polycyclic heteroaromatic compounds via quinone-methide intermediates is illustrated in Scheme 60. The required quinone-methides have also been generated from hydroxy-pyridones and -coumarins, and these have been allowed to react with a wide selection of aromatic amines. ... 

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