9,10-Dihydroanthracene, formation

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... 

Both Russell (5) and Barton (I) have examined the oxidation of dihydroanthracene in a solvent system consisting of 80% dimethyl sulfoxide and 20% tert-butyl alcohol and with potassium terf-butoxide as the base. In both studies, a large excess of base was used, so that there is a possibility of dicarbanion formation. In the present investigation, only catalytic amounts of base were used, which makes it unlikely that a... 

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. 

This study indicates that the oxidation of dihydroanthracene in a basic medium involves the formation of a monocarbanion, which is then converted to a free radical by a one-electron transfer step. It is postulated that the free radical reacts with oxygen to form a peroxy free radical, which then attacks a hydrogen atom at the 10-position by an intramolecular reaction. The reaction then proceeds by a free-radical chain mechanism. This mechanism has been used as a basis for optimizing the yield of anthraquinone and minimizing the formation of anthracene. 

Dr. Schowalter It appears that this is another mechanism that could account for the oxidation of dihydroanthracene without intermediate anthrone formation. 

Selective formation of ketones may be achieved through base-catalyzed oxidations.848 Transformation of 9,10-dihydroanthracene catalyzed by benzyltrimethy-lammonium hydroxide (Triton B)855 starts with proton abstraction ... 

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... 

In the presence of air at 5 °C, reaction of HGeCl3 with MA occurs in a different manner to give quantitatively the double germylation product rraws-9,10-bis(trichlorogermyl)-9-methyl-9,10-dihydroanthracene 35 (equation 33). A trans-configuration for 36 was suggested on the basis of comparison with an authentic sample of the ds-isomer obtained alternatively. This configuration is not sterically hindered and its formation can be ascribed to any mechanism. 

The reaction of oxazoles with alkynes is entirely different, leading to furans. The adducts (157) eliminate a cyanide in a retro-Diels-Alder process (equation 15). A typical example is the formation of the ester (164) from 5-ethoxy-4-methyloxazole and dimethyl acety-lenedicarboxylate (equation 16) equation (17) illustrates the production of two regioisomers in this reaction (79MI41802) a more elaborate case is the twofold addition of benzyne to 4-methyl-2,5-diphenyloxazole to give the bridged dihydroanthracene shown in equation (18) (80TL3627). 

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. 

Obara et al. (95) co-carbonized a petroleum pitch which gave a coke of mosaic size of optical texture with the strong Lewis acid catalyst, aluminium chloride,which promoted the size of the optical texture and extents of hydrogen transfer to added anthracene. A correlation was established between size of optical texture of the resultant cokes and extents of formation of 9,10-dihydroanthracene plus evolved hydrogen gas. 

The 9 and lo positions are the most unsaturated and hydrogenation leads to the formation of 9, lo-dihydroanthracene. Not only is the energy of activation for the hydrogenation reaction reduced by the increased unsaturation of the 9 and 10 carbon atoms, but the resulting molecule possesses considerable resonance energy by virtue of the two benzene rings and represents the most stable isomer of dihydroanthracene. 

Reduction of anthracene in the presence of an excess of acetic anhydride led to formation of the enol acetate of 9-acetyl-9,10-dihydroanthracene [293] ... 

Cyclooctatetraene gave stereoisomeric cis and trans) bicyclo[4,2,0]octane-7,8-diols and their diacetates in water and acetic acid, respectively [298,299], and the anodic acetoxylation of anthrancene resulted in the predominant formation of trans-9, lO-diacetoxy-9,10-dihydroanthracene [300]. 

A special reaction of this type is the formation of benzyne. o-Fluorobromobenzene reacts with lithium amalgam in ether or furan with an intermediate formation of benzyne. In the former medium, diphenylene and small amounts of triphenylene and 9,10-dimer-cura-9,10-dihydroanthracene were formed, whereas the major product (76%) in furan was 1,4-dihydronaphthalene-1,4-endoxide [64]. 

Ethyl formate, 64,65,233,287 Ethyl gjyoxylate, 374, 375 Ethyl 3-hydroxy-2-vinylisovalerate, 307 Ethyl methanesulfonate, 152 9-Ethyl-10-methyl-9,10-dihydroanthracene, 485... 

The cluster magnesium-anthracene adduct is extraordinarily active. Reactions are observed upon attempts to dissolve it even in such comparatively inert solvents as THF. CHsCh. toluene, or benzene. In these solvents, autohydrogenolysis takes places with the formation of dihydroanthracene and condensation products. The use as the solvent of CH2CI2 leads to polymers containing chlorine and use of THF leads to products of ring cleavage of the THF. 

Boyd, D.R., N.D. Sharma, R. Agarwal, R.A.S. McMordie, J.G.M. Bessems, B. van Ommen et al. (1993). Biotransformation of 1,2-dihydronaphtha-lene and 1,2-dihydroanthracene by rat liver microsomes and purified cytochromes P-450. Formation of arene hydrates of naphthalene and anthracene. Chem. Res. Toxicol. 6, 808-812. 

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). 

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