Phenanthrene 9,10-dihydrophenanthrene

Phenanthrene +H2 to dihydrophenanthrene Phenanthrene + 2H2 to tetrahydrophenanthrene Phenanthrene + 7H2 to perhydrophenanthrene Tetrahydrophenanthrene + 2H2 to octahydrophenanthrene Octahydrophenanthrene + 3H2 to perhydrophenanthrene... 

The reactions of tetrafluorobenzyne with 9,10-dihydrophenanthrene and phenanthrene yield the expected adducts formed by cyclo-addition at the 1,4-positions 90). The reaction of tetrafluorobenzyne with 1,6-methanocyclodecapentaene (52) was carried out in order to study the mass spectral and thermal fragmentation of (53) 90>. In the event benzocyclopropene and 1,2,3,4-tetrafluoronaphthalene (54) were formed. 

The photochemical isomerization of E-stilbenes has been applied in the preparation of phenanthrenes, as Z-stilbenes undergo electrocyclie ring closure (cf. chapter 3.1.3) to dihydrophenanthrenes which in turn are easily oxidized to phenanthrenes (3.1) 305). This sequence has also been employed in the synthesis of benzoquinolines 306) or of benzoquinolizines (3.2) 307). 

The most famous of these compounds is combretastatin A-4 (CA-4,7), isolated by Pettit et al. in 1989 [30]. Pettit s research led to the isolation and structural determination of a series of phenanthrenes, dihydrophenanthrene, stilbene, and bibenzyl compounds [31]. CA-4 (7), alongside CA-1 (8), was found to be an extremely active inhibitor of tubulin polymerization [30,32]. The major problems associated with these compounds were poor bioavailability and low aqueous solubility [33,34], and hence, research in the field was turned to designing better alternatives with the hope of eradicating the negative properties of these potent compounds. 

The 1H—NMR spectrum of 5,6,17,18-tetrahydro[2.2](2,7)phenan-threnopane (48) is compatible with the dihydrophenanthrene units being in an anti position. Dehydrogenation of 48 with 2,3-dichloro-5,6-dicyano-p-benzoquinone in benzene gave [2.2](2,7)phenanthrenophane which, owing to the similarity of its 1H—NMR spectrum to that of 2,7-dimethyl-phenanthrene, is assumed to have its phenanthrene units in the anti position 71>. 

Bezalel et al. (1996) reported that the white rot fungus Pleurotus ostreatus, grown in basidiomycetes rich medium, metabolized 94% of the phenanthrene added. Approximately 52% was converted to /rans-9,10-dihydroxy-9,10-dihydrophenanthrene (28%), 2,2 -diphenic acid (17%), and unidentified metabolites (17%). In addition, 3% was mineralized to carlaon dioxide. Sack et al. (1997) reported that phenanthrene was degraded by an Aspergillus niger sixain isolated from a mineral oil-contaminated soil in La Plata, Argentina. The major metabolite was identified via GC/MS as 1-methoxyphenanthrene. Two minor metabolites identified were 1- and 2-phenanthrol. 

When phenanthrene (0.65 mg/L) in hydrogen-saturated deionized water was exposed to a slurry of palladium catalyst (1%) at room temperature for approximately 2 h, 1,2,3,4,5,6,7,8-octahydro-phenanthrene and l,2,3,4,4a,9,10,10a-octahydrophenanthrene formed as products via the intermediates 1,2,3,4-tetrahydrophenanthrene and 9,10-dihydrophenanthrene, respectively (Schiith and Reinhard, 1997). 

Uses Explosives dyestuffs biochemical research synthesis of drugs preparation of 9,10-phen-anthrenequinone, 9,10-dihydrophenanthrene, 9-bromophenanthrene, 9,10-dibromo-9,10-dihydro-phenanthrene, and many other organic compounds. 

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. 

The submitter used a 65-cm. Podbielniak type column equipped with partial reflux head.6 For distillation of the sodium-treated phenanthrene the checkers employed a 6-in. Vigreux column. For the fractionation of the dihydrophenanthrene, the checkers employed a 15-cm. spinning-band column obtainable from Nester and Faust, Exton, Pennsylvania. 

Dihydrophenanthrene has been prepared from 2,2 -bis(bromomethyl)biphenyl and sodium 8 from the reduction of 2,2 -diiodobibenzy 1 in the presence of 1% palladium on barium carbonate catalyst 8 by the hydrogenation of phenanthrene in the presence of nickel8 or copper-chromium oxide catalyst 10 and by the coupling of 2,2 -bis(bromomethyl)biphenyl with lithium phenyl.11... 

The l,3,5-triene-l,3-cyclohexadiene interconversion is a six-electron electrocycli-zation that requires a cis central double bond to occur.245 An important application of this rearrangement is the photocyclization of cis-stilbene to dihydrophenanthrene [Eq. (4.45)], which is usually further oxidized to phenanthrene 249... 

There are a large number of photochemical cydizations of aromatic compounds that lead initially to polycyclic, non-aromatic products, although subsequent rearrangement, elimination or oxidation occurs in many instances to form aromatic secondary products. The archetype for one major class of photocydization is the conversion of stilbene to phenanthrene by way of a dihydrophenanthrene (3.60). 

Stilbenes and associated molecules provide very good examples of the formation of intermediate unstable isomers which give a chemical route for internal conversion. Upon irradiation, stilbenes undergo a cis-trans isomerization as the predominant reaction. However, under oxidative conditions phenanthrene is also formed.12 It was shown that the phenanthrene came only from c/s-stilbene (13),61 and that an intermediate unstable isomer, nms-dihydrophenanthrene (14), was the precursor of the phenanthrene.62-64 The dihydrophenarithrene was in its ground state, but vibrationally excited, and was formed by a process calculated to be endothermic by 33 10 kcal/mole-1.02 Oxygen or other oxidants converted it to phenanthrene (15), but in the absence of oxidants it was either collisionally stabilized or reverted to m-stilbene. 

In the vapor phase phenanthrene and hydrogen were products of the photolysis of c/.v-stilbene in addition to the expected mww-stilbene.65 The photolysis of 1,4-diphenyl-1,3-butadiene to give a-phenylnaphtha-lene is an analogous process.65 It was proposed that the intermediate dihydrophenanthrene was a cis form.66... 

One may well ask why the isomerization of alkenes discussed in the preceding section requires a sensitizer. Why cannot the same result be achieved by direct irradiation One reason is that a tt — tt singlet excited state (5,) produced by direct irradiation of an alkene or arene crosses over to the triplet state (Ij) inefficiently (compared to n —> it excitation of ketones). Also, the Si state leads to other reactions beside isomerization which, in the case of 1,2-diphenyl-ethene and other conjugated hydrocarbons, produce cyclic products. For example, cw-l,2-diphenylethene irradiated in the presence of oxygen gives phenanthrene by the sequence of Equation 28-8. The primary photoreaction is cyclization to a dihydrophenanthrene intermediate, 6, which, in the presence of oxygen, is converted to phenanthrene ... 

We know that C6-cyclization of 1-(naphthyl-2)-butene is possible without metal catalysts. The products are dihydrophenanthrene over quartz and 1,2,3,4-tetrahydrophenanthrene plus phenanthrene over alumina (50). The latter apparently catalyzes the redistribution of hydrogen in dihydrophenanthrene. Neither anthracene nor dihydro- or tetrahydroanthracene are formed over quartz or alumina from 1-(naphthyl-2)-butene. Plate and Erivanskaya concluded from this that the 2-alkylnaphthalene - anthracene reaction does not involve naphthylbutene intermediate (27). 

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