Aromatic compounds, fused

Substituents on benzene or benzenoid rings in fused pyridazines, i.e. in cinnolines and phthalazines, usually exhibit reactivity which is similar to that found in the correspondingly substituted fused aromatic compounds, such as naphthalene, and is therefore not discussed here. 

The latter reagent also methylates certain heterocyclic compounds (e.g., quinoline) and certain fused aromatic compounds (e.g., anthracene, phenanthrene). The reactions with the sulfur carbanions are especially useful, since none of these substrates can be methylated by the Friedel-Crafts procedure (11-12). It has been reported that aromatic nitro compounds can also be alkylated, not only with methyl but with other alkyl and substituted alkyl groups as well, in ortho and para positions, by treatment with an alkyllithium compound (or, with lower yields, a Grignard reagent), followed by an oxidizing agent such as Bra or DDQ (P- 1511). 

The ene-reaction, which is mechanistically related to the Diels-Alder reaction, has also been reported. The thermal addition of 3-ferf-butoxycarbonyl-2(3//)-oxazolone 236 to 2,2 -biindole 235 affords 4-(2,2 -biindol-3-yl)-2-oxazolidinone 237, probably via the indoline derivative. The product is further converted to the fused aromatic compound 238 by bromination with NBS and AIBN, followed by dehydrobromination (Fig. 5.58). ... 

Another type of supramolecular interaction of DNA is the intercalation of fused aromatic compounds into the stacked base pairs in double-stranded DNA (see Figure 6). Intercalation induces not only dehydration from the polar groups in intercalator but also concomitant unwinding, lengthening, dehydration, and stiffening of the DNA double helix. 

In general there is a good correlation between bond distances in fused aromatic compounds and bond orders. Another experimental quantity that correlates well with the bond order of a given bond in an aromatic system is the nmr coupling constant for coupling between the hydrogens on the two carbons of the bond.74... 

Naphthalene Naphthalene (C10H8) is the simplest fused aromatic compound, con- Hydrocarbons sisting of two fused benzene rings. We represent naphthalene by using one of the three Kekule resonance structures or using the circle notation for the aromatic rings. 

A clear difference between peroxyoxalate chemiluminescence and that of the previous compounds we have examined is that the emission wavelength is solely determined by the fluorophore and not by the oxalate ester. Typical fluorophores are fused aromatic compounds such as pyrene, anthracene, and, especially, per-ylene. 

A sequence involving the same elementary steps but in a different order has been designed by Chuang [73] to prepare fused aromatic compounds. Examples of domino reactions, where an allyl sulfide moiety is introduced purposely in order to induce the y -fragmentation of a radical intermediate, are numerous [74]. One... 

A novel ring-opening reaction of oxirans, catalysed by copper and pyridine, generates c/s-diols under mild conditions. The bicyclic epoxides (186 = 1 or 2) yield (187 n = 1) (95%) and (187 = 2) (85%) in neutral, phosphate-buffered, solution. This type of reaction may have some relevance to the metabolic pathways for fused aromatic compounds, which are thought to proceed via arene oxides and diol epoxides. The catalyst system may be used to add OH", Cr, or MeO regiospecifically to the benzylic centre of indene oxide, with proton addition to the oxygen atom of oxiran. 

The Catellani s alkylation-alkenylation sequence using norbomene offers a useful synthetic method for 2,6-dialkylated 1-substituted benzenes. Lautens applied the reaction to the synthesis of fused aromatic compounds using ort/jo-substituted iodobenzenes and bromoalkenes. Reaction of o-iodotoluene (11) with ethyl 6-bromo-2-hexenoate (13) afforded the benzocarbocycle 14 via monoalkylation and intramolecular Heck reaction. It is important to use tri-2-furylphosphine (1-3) as a ligand [4]. Similarly the 2,5-disubstituted 4-benzoxepine 17 was obtained in 72% yield by the reaetion of 1-iodonaphthalene (15) with the unsaturated bromo ester 16 [5]. 

Various carbene complexes Cr(CO)5 =C(OMe)CR =CHR2 react with HC=C(CH2)4CN by benzannulation and subsequent intramolecular addition processes to form spirocyclic or fused aromatic compounds depending upon how the reaction is quenched. The reactions of various p-aminovinyl carbene complexes M(CO)5 =C(OEt)CH=CR(NHRi) (M = Cr, W) with alkynes R CaCH results in loss of ethanol and the formation of pyiidinylidene derivatives 53. These undergo protonation which results in replacement of the metal by a proton and the formation of the corresponding pyridinium salts. i ... 

Anodic oxidation of various aromatic compounds Uke anisole, mesitylene, and fused aromatic compounds like naphthalene and anthracene was carried out in various ionic liquids such as [BMIM][PF6] and [BMIM][NTf2] to provide the corresponding dimmers in moderate to good yields [25]. Under similar conditions, anodic oxidation of 1,2-dimethoxybenzene leads to the corresponding trimer as shown in Scheme 7 [25]. 

Photochemical trans-cis isomerization of diarylethenes followed by photochemical 6ic electrocyclization and oxidation is a standard protocol, and this protocol is widely applied in the synthesis of angularly fused aromatic compounds [4]. In particular, this strategy is widely used in the synthesis of helicenes, an important class of angularly fused polycyclic aromatic compounds (Scheme 16.11) [14]. 

Ag2C03 in the arylation of thiophenes with iodoarenes. This is a remarkably general phenomenon, applicable to unsubstituted, monosubstituted, and disubstituted thiophene derivatives, as well as thiophene-containing fused aromatic compounds (eq 3). ... 

Miyano and coworkers reported the carboxylation of fused aromatic compounds with carbon dioxide catalyzed by AlBr3 (Scheme 6.8) [10]. Although yields are moderate, the reaction proceeds regioselectively similar to the Friedel-Crafts acylation reaction. 

Fused aromatic compounds such as polyacenes have attracted much attention as organic conductive materials. However, established methods are very limited. Lack of general and convenient synthetic methods for fused aromatic compounds and their very poor solubility in organic solvents are the most serious problems that control further advances in this very important field. Taka-hashi and coworkers have recently developed a synthetically useful method for preparation of fused aromatic compounds, by using the zirconocene-mediated aromatization of alkynes. In order to solve the solubility problem, alkyl substituents are introduced into to the skeletons. In principle, two types of synthetic protocols have been used. Type I protocol is via the homologation starting from a functionalized benzene derivative (Scheme 3) [75] the Type II protocol is via the intermolecular cycloaddition of two alkynes to an arene (Scheme 4) [76]. 

Figure 6.8 An example of prefix-suffix nomenclature of fused aromatic compounds. Note that the numbers within the bracket refer to positions on the prefix ring, whereas the letters are associated with bonds within the suffix ring.

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