Dihydroanthracene, from anthracene

Boyland, E. and Levi, A.A. (1935) Metabolism of polycyclic compounds production of dihydroxy-dihydroanthracene from anthracene. Biochemical Journal, 29 (12), 2679-2683. 

Examples include luminescence from anthracene crystals subjected to alternating electric current (159), luminescence from electron recombination with the carbazole free radical produced by photolysis of potassium carba2ole in a fro2en glass matrix (160), reactions of free radicals with solvated electrons (155), and reduction of mtheiiium(III)tris(bipyridyl) with the hydrated electron (161). Other examples include the oxidation of aromatic radical anions with such oxidants as chlorine or ben2oyl peroxide (162,163), and the reduction of 9,10-dichloro-9,10-diphenyl-9,10-dihydroanthracene with the 9,10-diphenylanthracene radical anion (162,164). Many other examples of electron-transfer chemiluminescence have been reported (156,165). 

Akhtar MN, DR Boyd, NJ Thompson, M Koreeda, DT Gibson, V Mahadevan, DM Jerina (1975) Absolute stereochemistry of the dihydroanthracene-ci - and -fra 5,l,2-diols from anthracene by mammals and bacteria. J Chem Soc Perkin I 2506-2511. 

Jerina, D. M. (1975). Absolute stereochemistry of the dihydroanthracene-dr- and tram-1,2-diols produced from anthracene by mammals and bacteria. Journal of the Chemical Society Perkin Transactions, 1975, 2506-11. 

The photo-oxidation of n-butane has been modelled by ab initio and DFT computational methods, in which the key role of 1- and 2-butoxyl radicals was confirmed.52 These radicals, formed from the reaction of the corresponding butyl radicals with molecular oxygen, account for the formation of the major oxidation products including hydrocarbons, peroxides, aldehydes, and peroxyaldehydes. The differing behaviour of n-pentane and cyclopentane towards autoignition at 873 K has been found to depend on the relative concentrations of resonance-stabilized radicals in the reaction medium.53 The manganese-mediated oxidation of dihydroanthracene to anthracene has been reported via hydrogen atom abstraction.54 The oxidation reactions of hydrocarbon radicals and their OH adducts are reported.55... 

Orchin (149) has described a novel method for the preparation of small quantities of tetrahydroanthracene from 9,10-dihydroanthracene or from anthracene. 

Carbonization of Anthracene. The pyrolysis of anthracene has been investigated extensively (13-17). The initial reaction is not well-understood, and various radical intermediates have been proposed. The thermodynamics of anthracene dissociation has been discussed by Stein (8), and the formation of the anthryl radical by a disproportionation reaction such as Scheme II is expected to be very slow because of the instability of the a radical (1). A mechanism involving the direct formation of the anthryl radical by hydrogen dissociation, although not favorable, might be possible. A reaction scheme based on the formation of the radical (2) from anthracene and dihydroanthracene has also been proposed (17). 

Anthracene dimers as well as dihydroanthracene have been identified as initial reaction products in all pyrolysis studies of anthracene. As shown in Chart I, 11 dimers from anthracene are possible. Because the 9-position is the most reactive, one might expect a predominance of the 9,9 -dimer. However the 2,9-dimer was reported as the major product in one study (18). Many of the other possible dimers were also obtained, depending on the reaction conditions employed. Both steric effects and reactivity factors must, therefore, be taken into account for considering the possible reaction products in aromatic hydrocarbon pyrolysis. The results for anthracene show how the lack of a functional group and the nonspecificity for molecular recombination lead to complex product mixtures in aromatic pyrolysis. 

Partial reduction of polyarenes has been reported. Use of boron trifluoride hydrate (BF3 OH2) as the acid in conjunction with triethylsilane causes the reduction of certain activated aromatic systems 217,262 Thus, treatment of anthracene with a 4-6 molar excess of BE3 OH2 and a 30% molar excess of triethylsilane gives 9,10-dihydroanthracene in 89% yield after 1 hour at room temperature (Eq. 120). Naphthacene gives the analogously reduced product in 88% yield under the same conditions. These conditions also result in the formation of tetralin from 1-hydroxynaphthalene (52%, 4 hours), 2-hydroxy naphthalene (37%, 7 hours), 1-methoxynaphthalene (37%, 10 hours), 2-methoxynaphthalene (26%, 10 hours), and 1-naphthalenethiol (13%, 6 hours). Naphthalene, phenanthrene, 1-methylnaphthalene, 2-naphthalenethiol, phenol, anisole, toluene, and benzene all resist reduction under these conditions.217 Use of deuterated triethylsilane to reduce 1-methoxynaphthalene gives tetralin-l,l,3-yielding information on the mechanism of these reductions.262 2-Mercaptonaphthalenes are reduced to 2,3,4,5-tetrahydronaphthalenes in poor to modest yields.217 263... 

The major oxidation product isolated was anthracene, perhaps formed in part from the hydroperoxide (I). However, significant amounts of potassium superoxide accompanied the anthracene. This result suggests that the major source of anthracene involved the oxidation of the dianion. In pure DMSO in the presence of excess potassium tert-butoxide, a trace of oxygen converts 9,10-dihydroanthracene, 9,10-dihy-drophenanthrene, or acenaphthene to the hydrocarbon radical anions. These products are apparently formed in the oxidation of the hydrocarbon dianions. 

Isolation of Oxidation Products. After oxygen absorption had ceased, or reached the desired value, the oxidates were poured into water. In many cases the reaction product could be removed by filtration in high yield. In this manner xanthone (m.p. 172-174°C.), was isolated from oxidations of xanthene or xanthen-9-ol thioxanthone (m.p. 208-210°C.), from thioxanthene acridine (m.p. 107-109°C.), from acridan anthracene (m.p. 216-217°C.), from 9,10-dihydroanthracene phenanthrene (m.p. 95-99°C.), from 9,10-dihydrophenanthrene pyrene (m.p. 151-152.5°C.) (recrystallized from benzene) from 1,2-dihydropyrene and 4-phenan-throic acid (m.p. 169-171 °C.) (recrystallized from ethanol) by chloroform extraction of the hydrolyzed and acidified oxidate of 4,5-methyl-enephenanthrene. 

Anthrone did not react with DMSO under the reaction conditions. However, 9,10-anthraquinone (2 mmoles) in 25 ml. of DMSO (80%)-terf-butyl alcohol (20% ) containing potassium tert-butoxide (4 mmoles) gave a deep red solution at 25°C., from which 60% of the adduct could be isolated after 1 hour and 88% after 3 hours. This adduct was isolated from the oxidate of 9,10-dihydroanthracene (after hydrolysis, acidification, and filtrations of anthracene) by extraction of the aqueous filtrate by chloroform. Xanthone and thioxanthone failed to form isoluble adducts with DMSO in basic solution. 

The autoxidation mechanism by which 9,10-dihydroanthra-cene is converted to anthraquinone and anthracene in a basic medium was studied. Pyridine was the solvent, and benzyl-trimethylammonium hydroxide was the catalyst. The effects of temperature, base concentration, solvent system, and oxygen concentration were determined. A carbanion-initi-ated free-radical chain mechanism that involves a singleelectron transfer from the carbanion to oxygen is outlined. An intramolecular hydrogen abstraction step is proposed that appears to be more consistent with experimental observations than previously reported mechanisms that had postulated anthrone as an intermediate in the oxidation. Oxidations of several other compounds that are structurally related to 9,10-dihydroanthracene are also reported. 

The direct reaction of oxygen with the carbanion from dihydroanthracene does not seem likely. Russell (5) has indicated a preference for a one-electron transfer process to convert the carbanion to a free radical, which then reacts with oxygen to form an oxygenated species. Therefore, we considered a mechanism involving one-electron transfer to form a free radical from the carbanion, which would lead to the formation of anthraquinone and anthracene without having either the hydroperoxide or anthrone as an intermediate. 

Miyazawa et al. (92) related rates of decrease of aliphatic hydrogen protons during pyrolysis of ethylene tar pitch to formation of mesophase. Yokono et al, (93) used the model compound anthracene to monitor the availability of transferable hydrogen. Co-carboniza-tions of pitches with anthracene suggested that extents of formation of 9,10-dihydroanthracene could be correlated with size of optical texture. The method was then applied to the carbonization behaviour of hydrogenated ethylene tar pitch (94). This pitch, hydrogenated at 573 K, had a pronounced proton donor ability and produced, on carbonization, a coke of flow-type anisotropy compared with the coarse-grained mosaics (<10 ym dia) of coke from untreated pitch. 

Another significant technique developed by Sanada s group is the characterization of pitch for its electron donor ability, which is estimated by the amount of hydrogen transferred from pitch to anthracene after the mixture has been heated to 400°C (22). The present authors later showed that the electron acceptor ability of pitch can be estimated in a similar manner by using a mixture of pitch and dihydroanthracene (23). The details of hydrogen transfer between pitch molecules is an important topic for study to understand the initial stages of carbonization processes. 

Anthracene hydride (the anion derived from 9,10-dihydroanthracene) reacts rapidly with chalcone to form an anionic Michael adduct along with a chalcone dimerization product (Scheme 83). Prolonged reaction in the presence of anthracene hydride cleaves the Michael adduct into anthracene and the enol-ate of the saturated ketone. The partial structure RCCCO is essential for this fragmentation, as mesityl oxide, for example, gave only the Michael adduct. 

Figure 27. Application of flow cell and UV spectroscopy to study the reduction of aromatic compounds in iV,iV-dimethylformamide/0.1 M BU4NBF4 a) Plot of absorbance at = 556 nm and 732 nm, of the products obtained in the reduction of anthraquinone (T) and anthracene ( ), respectively, as the galvanostatic current to the flow cell is increased and a continuous flow of 5 mL min is maintained. The substrate concentrations are both 0.1 mM and the light path is 1 cm b) and c) The absorption spectra of the product obtained from reduction of anthraquinone and anthracene, respectively, when the galvanostatic current is increased above the maximum required for generating the radical anion. The current is increased from 2.0 to 2.8 mA in steps of 0.2 mA and the development in the spectra is indicated with arrows. Isosbestic points are also indicated. For anthraquinone, the spectra of the radical anion and the dianion could be resolved whereas for anthracene the dianion is protonated and spectra of the radical anion and 9,10-dihydroanthracen-9-ide could be resolved [65].

Two methods have evolved for the generation of 147r-electron, aromatic heterocyclic derivatives of anthracene. In the first approach neutral derivatives are obtained by a 9,10-HCl elimination from the dihydroanthracene derivative (B, Si, P, As) in the second method, anions are generated by proton abstractions from the neutral saturated heterocycle (B, Si). 

Benzynes and substituted benzynes react with isoindoles to give the 9,10-dihydroanthracene-9,10-imines (92).33 A considerable number of substituted compounds of this type have been prepared.27 Triptycene derivatives (i.e., the benzyne adducts of the anthracene system) have been encountered as unexpected products from the reaction of benzyne with 2-benzyl-1,3,4,7-tetramethylisoindole.114... 

Bromine adducts in which not all the C=C bonds are saturated are more easily prepared from polycyclic aromatic hydrocarbons. Thus 1,2,3,4-tetra-bromo-l,2,3,4-tetrahydronaphthalene is obtained by brominating pure naphthalene in anhydrous CC14 at 0° with irradiation (30% yield)134 or in CC14 at room temperature with irradiation and addition of peroxide (ascaridole) (12% yield).135 Anthracene adds bromine in CS2 at 0°, giving 9,10-dibromo-9,10-dihydroanthracene,136,137 and phenanthrene in ether138 or carbon disulfide139 gives 9,10-dibromo-9,10-dihydrophenanthrene when warmed, these two products pass into 9-monobromo derivatives by loss of HBr. 

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