Polynuclear aromatic compounds synthesis

A Dotz benzannulation reaction was utilized in the synthesis of the furo[2,3- >]furan core of aflatoxin B2 as illustrated below <06TL2299>. Synthesis of polynuclear aromatic compounds was achieved by using [5+5] cycloaddition of 2-alkynylarylcarbene complexes and enyne-aldehyde derivatives <06TL5303>. 

The reaction is considered to arise from the stilbene singlet 7t,7t excited state and is useful for the synthesis of a great variety of polynuclear aromatic compounds, such as helicenes and large [n]phenacenes (n = 3 up to n = 7) [25], The arene positions involved in photocyclization are predictable the preferred route corresponds to the dihydro intermediate with the higher degree of aromaticity (Scheme 9.18). 

Aromatization is important in both synthesis and analysis. Many polynuclear aromatic compounds are made from open-chain compounds by ring closure the last step in such a synthesis is aromatization (see, for example, Secs. 30.14, 30.19, and 31.13). Many naturally occurring substances are hydroaromatic ... 

Weyand EH, Amin S, Sodhi R, et al. 1991c. Effects of methyl substitution on the metabolism and binding of benz[e]acephenanthrylene. In Garriques P, Lamotte M, eds. Polycyclic aromatic compounds. Synthesis, properties, analytical measurements, occurence, and biological effects. Proceedings of the thirteenth international symposium on polynuclear aromatic hydrocarbons. Philadelphia, PA Gordon and Breach. 

Another useful sequence that produces polynuclear aromatic compounds is the Bally-Scholl synthesis. This variation involves addition of a glycerol derivative (a 1,2,3-propanetriol) to an aromatic ring, usually an... 

Synthesis of polynuclear aromatic compounds incorporating a fused thiophene ring 05H(65)1491. 

Abstract This chapter summarizes the synthesis, physical properties, structure, and crystal packing of buckybowls. Buckybowls exemplify an intermediate class of polynuclear aromatic compounds between the closed-shell fullerenes and the flat extended arrays of graphene. These warped sheets can be seen as fragments of fullerenes or the end cap of single-waUed carlxMi nanotubes and, their curvature endows them with physical properties distinct from flat polynuclear hydrocarbons, which opens up unique possibilities for molecular bowls in various organic materials applications. 

Presently the major step in the GTL conversion is considered to be the Fischer-Tropsch synthesis of hydrocarbons from synthesis gas (CO-I-H ). The classical processes produce waxes (solid hydrocarbons) that are further upgraded into the components of liquid fuels (gasoline, diesel). Diesel production by this technology seems to be the best solution. The synthetic diesel fuel has better characteristics compared to the fuel grades produced from oil (standard EN-590) the cetane number is 75 (versus 55 for the oil-derived diesel) the content of polynuclear aromatic compounds is 0.1 (versus 6%) the sulfur content is 0 ppm (versus 50 ppm). Such synthetic fuels can be used as additives to the oil-based diesel. GTL-diesel is used in Germany, Austria, and Sweden and the blends of the synthetic fuel and conventional diesel are used in France, Italy, and other countries. 

The Suzuki cross-coupling reaction is recognized as a novel, abbreviated method for the synthesis of 2-hydroxychrysene, 2-hydroxy-5-methylchrysene, and 8-hydroxy-5-methyl-chrysene from easily accessible reactants (Eq. (8)) [23]. These phenolic compounds constitute precursors for the synthesis of dihydrodiol and bay-region diol epoxide derivatives of chrysene and 5-methylchrysene, which are implicated as the active forms of carcinogenic polynuclear aromatic hydrocarbons. 

This synthesis is applicable to many aromatic compounds, including alkoxyl or N,N dimethylamino derivatives of benzene and naphthalene, naphthols, indole, and certain reactive hydrocarbons, namely, anthra-cene, 1,2-benzanthracene, 3,4-benzpyrene, ° and pyrene. The high-melting polynuclear hydrocarbons react best in the presence of a solvent, such as o-dichlorobenzene. For example, a solution of anthracene, methyl formanilide, and phosphorus oxychloride in o-dichlorobenzene is heated 1 hour at 90-95° then an aqueous solution of sodium acetate is added, and the solvent and N-methylaniline are removed by steam distillation. The solid residue is readily purified to yield 9-anthraldehyde (84%). With liquid or low-melting compounds a solvent is not required. 

In addition, the occurrence of picene derivatives as well as similar polynuclear aromatic systems (White, 1983) in the solvent extracts of coal might be cited as evidence for the inclusion of sterane-type materials in the precursor material to coal. This does assume that the skeletal structure remains intact throughout the maturation process and that there has been no degradation or even formation of new skeletal systems. Indeed, the biosynthesis of aromatic compounds is well documented, including the synthesis of aromatic species from nonaromatic precursors (Weiss and Edwards, 1980 Lee et al., 1981). 

This aldehyde synthesis is applicable to compounds of the aromatic series having a labile hydrogen atom (phenyl ethers,1 naphthols,2 dialkylanilines,3-4 naphthostyril,2 anthrones 2) and to certain hydrocarbons of requisite reactivity (anthracene,5-6 7 1,2-benzanthracene,6 3,4-benzpyrene,3 7 pyrene,8 styrene,9 and a, a-diarylethylenes 9). With polynuclear hydrocarbons the best results are secured by the use of a solvent such as o-dichloro-benzene. 9-Anthraldehyde has also been prepared by the action of hydrogen cyanide and aluminum chloride on anthracene in chlorobenzene.10... 

Many completely aromatic polynuclear hydrocarbons are readily formed by cyclization of aryl-substituted aldehydes, ketones, or related compounds. The simplest case is the formation of naphthalene by refluxing (fi-styrylacetaldehyde, C HsCH = CHCH2CHO, with hydrobromic acid-acetic acid mixture. " The ring closure has found extensive use in the synthesis of 9-alkyl- and 9 aryl-anthracenes and phenanthrenes. " ... 

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