Chrysenes, formation

Diketones 29 are not intermediates in the formation of chrysenes because under the reaction conditions they form only a-naphthols 204, which are products of intramolecular cyclization. The real intermediate for chrysene formation is the anhydrobase 267. The key role of this compound is supported by the isolation of the dimeric pseudobase 269 (85KGS910), as well as by trapping of the latter compound with the proton sponge, which possesses pronounced basic properties (68CC723). 

Whereas peri methyl substitution does not block dihydrodiol formation in the adjacent ring in the benz[a]anthracene system (38,39), it apparently does so in the chrysene system. 7,8-Dihydro-... 

Analogous results have been recently obtained with trans-1,2-dihydroxy-ant i-3, 4-epoxy- 1,2,3,4-tetrahydro-5-methy1 chrysene (13) and the epoxide 1-oxyrany1pyrene (14). Thus, the formation of non-covalent intercalative site I complexes appears to be a general phenomenon which governs the interaction of polycyclic aromatic epoxides with DNA (15-17). 

Nucleophilic Trapping of Radical Cations. To investigate some of the properties of Mh radical cations these intermediates have been generated in two one-electron oxidant systems. The first contains iodine as oxidant and pyridine as nucleophile and solvent (8-10), while the second contains Mn(0Ac) in acetic acid (10,11). Studies with a number of PAH indicate that the formation of pyridinium-PAH or acetoxy-PAH by one-electron oxidation with Mn(0Ac)3 or iodine, respectively, is related to the ionization potential (IP) of the PAH. For PAH with relatively high IP, such as phenanthrene, chrysene, 5-methyl chrysene and dibenz[a,h]anthracene, no reaction occurs with these two oxidant systems. Another important factor influencing the specific reactivity of PAH radical cations with nucleophiles is localization of the positive charge at one or a few carbon atoms in the radical cation. 

The carcinogenicity of PAH with relativelyTigh IP, such as benzo[c]phenanthrene, benz[a]anthracene, chrysene, 5-methyl chrysene and dibenz[a,h]anthracene (Table I), can be related to the formation of bay-region diol epoxides catalyzed by monooxygenase enzymes (j>). However, the most potent carcinogenic PAH have IP < ca. 7.35 eV. 

AI3-00040, see Cyclohexanol AI3-00041, see Cyclohexanone AI3-00045, see Diacetone alcohol AI3-00046, see Isophorone AI3-00050, see 1,4-Dichlorobenzene AI3-00052, see Trichloroethylene AI3-00053, see 1,2-Dichlorobenzene AI3-00054, see Acrylonitrile AI3-00072, see Hydroquinone AI3-00075, see p-Chloro-rrr-cresol AI3-00078, see 2,4-Dichlorophenol AI3-00085, see 1-Naphthylamine AI3-00100, see Nitroethane AI3-00105, see Anthracene AI3-00109, see 2-Nitropropane AI3-00111, see Nitromethane AI3-00118, see ferf-Butylbenzene AI3-00119, see Butylbenzene AI3-00121, see sec-Butylbenzene AI3-00124, see 4-Aminobiphenyl AI3-00128, see Acenaphthene AI3-00134, see Pentachlorophenol AI3-00137, see 2-Methylphenol AI3-00140, see Benzidine AI3-00142, see 2,4,6-Trichlorophenol AI3-00150, see 4-Methylphenol AI3-00154, see 4,6-Dinitro-o-cresol AI3-00262, see Dimethyl phthalate AI3-00278, see Naphthalene AI3-00283, see Di-rj-butyl phthalate AI3-00327, see Acetonitrile AI3-00329, see Diethyl phthalate AI3-00399, see Tributyl phosphate AI3-00404, see Ethyl acetate AI3-00405, see 1-Butanol AI3-00406, see Butyl acetate AI3-00407, see Ethyl formate AI3-00408, see Methyl formate AI3-00409, see Methanol AI3-00520, see Tri-ocresyl phosphate AI3-00576, see Isoamyl acetate AI3-00633, see Hexachloroethane AI3-00635, see 4-Nitrobiphenyl AI3-00698, see IV-Nitrosodiphenylamine AI3-00710, see p-Phenylenediamine AI3-00749, see Phenyl ether AI3-00790, see Phenanthrene AI3-00808, see Benzene AI3-00867, see Chrysene AI3-00987, see Thiram AI3-01021, see 4-Chlorophenyl phenyl ether AI3-01055, see 1.4-Dioxane AI3-01171, see Furfuryl alcohol AI3-01229, see 4-Methyl-2-pentanone AI3-01230, see 2-Heptanone AI3-01231, see Morpholine AI3-01236, see 2-Ethoxyethanol AI3-01238, see Acetone AI3-01239, see Nitrobenzene AI3-01240, see I idine AI3-01256, see Decahydronaphthalene AI3-01288, see ferf-Butyl alcohol AI3-01445, see Bis(2-chloroethoxy)methane AI3-01501, see 2,4-Toluene diisocyanate AI3-01506, see p,p -DDT AI3-01535, see 2,4-Dinitrophenol AI3-01537, see 2-Chloronaphthalene... 

Kinetic data on the oxepin-benzene oxide equilibration have been obtained from the temperature-dependent NMR studies. Low values were observed for the enthalpy of isomerization of oxepin (7.1 kJ mol-1) and 2-methyloxepin (1.7 kJ mol-1) to the corresponding benzene oxides (67AG(E)385). The relatively small increase in entropy associated with oxepin formation (5-11 J K 1 mol-1) is as anticipated for a boat conformation in a rapid state of ring inversion. Thermal racemization studies of chrysene 1,2- and 3,4-oxides have allowed accurate thermodynamic parameters for the oxepin-arene oxide equilibration process in the PAH series to be obtained (81CC838). The results obtained from racemization of the 1,2- (Ea 103.7 kJ mol-1, AS 3.7 JK-1 mol-1 and 3,4- (Ea 105.3 kJmoF1, AS 0.7 J K"1 mol ) arene oxides of chrysene are as anticipated for the intermediacy of the oxepins (31) and (32) respectively. 

The use of elevated temperature at the beginning of this reaction leads to the formation of chrysenes, as described in Section IlI,F,2,b. 

Therefore, most probably, the formation of chrysenes 246 from 2-benzopyrylium salts occurs via the process of a-1 dimerization. At the same time, one cannot exclude the action of anhydrobase 267 as dieno-phile, which leads to its addition to positions 1 and 4 of the initial 2-benzopyrylium cation by analogy with [4 + 2] cycloadditions in reaction with ethyl vinyl ether (Scheme 14) (cf. Section III,D,1). 

The formation of acyl-chrysenes 270 from 1-methyl-substituted ben-zo[c]pyrylium salts 266 occurs not only on heating in alkaline solutions, but also in acidic nucleophilic media (cf. Section III,C,4,b,i). However, in the latter case, together with acylchrysenes 270, their deacylated analogs 273 are formed (85KGS910). Under these conditions, the same results were obtained for conversions of diketones 29, therefore it is difficult to conclude which compound (anhydrobase 267 or diketone 29) is the intermediate in the formation of chrysenes 270 and 273 from salts 266 in acidic nucleophilic medium. It was not possible to trap or detect the dimeric pseudobase 269 under these conditions. However, the latter compound, under the described conditions or on heating in acetic acid, forms the mixture of the same products (270 and 273). 

The pathway to chrysenes, in this case, was assumed to include the formation of dimeric salts 268. Then the intramolecular interfragment interaction takes place with the formation of the C4b—CiA bond, which leads to the already familiar intermediate 272 (Scheme 14). 

The formation of deacylated derivatives 273 in acidic media may be explained by ipjo-protonation of acyl-chrysenes 270. On the other hand, they may also be explained by reactions at preceding stages by analogy with transformations known for monocyclic pyrylium salts (68TL4379 69JOC2736 72TL4439) (cf. Section III,C,4,d and III,F,2,c). Chrysenes... 

Thus, dimer 276 is obtained from salt 30 at room temperature in a diphase system of 10% aqueous solution of sodium hydroxide and ether. On heating with alkali in isopropyl alcohol, these dimers are converted quantitatively into benz[a]anthracenes 278 (88KGS1185), and likewise the formation of dihydro-derivatives of chrysenes 271 (85KGS910) and 277... 

Many polycyclic aromatic amines and aldehydes are commercially available, but their supply is very limited. Preparation of these starting materials is necessary for studying the (3-lactam formation reaction [93]. Nitro compounds are the precursors for the amines. An important task was to prepare polycyclic aromatic nitro compounds, particularly those of chrysene, phenanthrene, pyrene, and dibenzofluorene in good yield. Nitration of these hydrocarbons with concentrated nitric acid in sulfuric acid is a widely used reaction for this purpose. Our research culminated in facile synthesis of polyaromatic nitro derivative 9 starting from polyaromatic hydrocarbons (PAHs) 8 through the use of bismuth nitrate impregnated with clay (Scheme 1) ([94, 95] for some examples of bismuth nitrate-catalyzed reactions... 

Extensive studies have been conducted to investigate the formation of chiral columns or helical superstructures in chiral and nonchiral disk- [53], star- [54, 55], and board-shaped [56] molecules. However, spontaneous deracemization has never been unambiguously demonstrated in discotic columnar phases consisting of nonchiral or racemic molecules. We recently observed clear evidence showing chiral resolution in a disk-like molecules with a dibenzo[g,p]chrysene core [57]. 

The mechanism of this reaction shows that excitation of the substrate gave an n,n triplet state, but this excited state was unable to dissociate the carbon-iodine bond. This was demonstrated by showing that the n,n triplet state, when sensitized by chrysene, did not produce coupling products. Probably, the reaction occurred in an excited a,a triplet state mainly localized on the carbon-iodine bond, and the interaction between this triplet state and aromatic compounds led to homolytic cleavage of the C-I bond with the formation of both a 5-thienyl radical and a complex between the aromatic compound and the halogen atom. The formation of this complex was demonstrated by the presence of a short-lived transient with Amax = 510 nm, showing a second-order decay kinetics and a half-life of ca. 0.4 (is in laser flash photolysis. The thienyl radical thus formed... 

Apart from the construction of phenanthrenes, carbene complexes have also been used for the synthesis of more extended polycyclic arenes. An unusual dimerization of chromium coordinated ortbo-ethynyl aryl carbenes results in the formation of chrysenes (Scheme 37) [81]. This unusual reaction course is presumably due to the rigid C2 bridge that links the carbene and alkyne moieties, and thus prevents a subsequent intramolecular alkyne insertion into the metal-carbene bond. Instead, a double intermolecular alkyne insertion favored by the weak chromium-alkyne bond is believed to occur forming a central ten-membered ring that may then rearrange to the fused arene system. For example, under typical benzannulation conditions, carbene complex 97 affords an equimolar mixture of chrysene 98a and its monochromium complex 98b. The peri-interactions between the former alkyne substituent (in the 5- and 11-positions) and the aryl hydrogen induce helicity in the chrysene skeleton. 

Figure 3 shows the results obtained with pyrene and substituted pyrenes. It is seen that the position and number of substituents do not affect the adsorption. Similar results were obtained in studies of chrysenes, benzopyrenes and also benzonaphthothiophene. This indicates that polyaromatic species without nitrogen heteroatoms are adsorbed via the tt-electrons in the large aromatic sheets, and thereby adsorption is unaffected by the degree of substitution. This shows that the sulfur does not play a part in the initial adsorption or coke formation. 

Structural effects the free volume model. Demonstrative examples of the role of free spaces on Ps formation in solids are provided by solids in which no Ps is formed when pure, and where the Ps yield increases as some dopant impurity is added. This is the case for p-terphenyl, in which the Ps yield increases as either chrysene or anthracene are added. Both dopant molecules, when introduced in the p-terphenyl matrix, promote the formation of extrinsic defects having roughly the size of a naphthalene molecule [42], Similarly, doping the ionic KIO4 matrix by lOj ions induces the formation of oxygen vacancies which promote the formation of Ps [43],... 

Acid-catalysed rearrangement/hydrolysis of the 3a,20a-disulphate (168) gave the 17/3-methyl-18-nor-compound (169). Rearrangement of the 17a-hydroxy-3-oxo-A -triene (170) to the c-ring aromatic compound (171) occurred in formic acid as did the rearrangement of 17a-ethynyloestradiol to the chrysene derivative (172). The 9,ll-epoxy-17-hydroxy-steroids (173) and (174) were converted with BF3-Et20 into the C-ring aromatic compounds (175) and (176) respectively. " Normal acetonide formation in the reaction of... 

The combination of a large number of chemical resolution and assignment studies (Table 3) of benzo-ring /rans-dihydrodiols along with studies designed to define the stereochemical course of metabolism of benzo[a]pyrene, ° benz[a]-anthracene, chrysene, phenanthrene, benzo[c]phenanthrene, anthracene, and naphthalene has led to the conclusion that the combined action of cytochrome P450c and epoxide hydrolase has a marked preference for the formation of (—)-(R,R)-dihydrodiols. This result pertains even when the initially... 

The role of free volume on TICT emission of dimethylaminobenzonitrile and related compounds has been examined in polymeric media . The increase in emission with increase in free volume rules out the possibility of specific solute-solvent interactions being responsible for TICT emission in PVA polymer matrices. Fluorescence quenching of phenanthrene and chrysene by KI in met ha nol-et ha no.l, s olu t ion s shows both electron transfer processes and exciplex formation between aromatic hydrocarbon and perturber are important. ... 

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