Polycyclic aromatic systems

Studies of solvolysis of similar polyfluonnated polycyclic aromatic systems, such as 2,3-(tetrafluorobenzo)bicyclo[2 2 2]octadienes and related compounds, proved the ionic mechanism of this rearrangement [55, 36, 37] (equation 9) Possible nonclassical carbonium ion involvement has been discussed [5S, 39, 40, 41]... 

Divinylnaphthalenes 63 and 64 (Figure 2.8) react with strong dienophiles and have been used to synthesize complex polycyclic aromatic compounds [60], While 2-vinylnaphthalene (61) and 1-vinylnaphthalene (62) act as 47t components, 3-vinylphenanthrene (65) and 1- vinylpyrene (66) (Figure 2.8), characterized by an extended polycyclic aromatic system, preferentially undergo [2- -2] cycloaddition [57, 61, 62]. 

Heterocyclic Ring Systems (Unsaturated) and Polycyclic Aromatic Systems... 

Table 5.5 Chemical shifts and couplings in some common heterocyclic and polycyclic aromatic systems.

Energetic attempts are being made at this time by Coulson, Daudel, Pullman and others to refine the theory of electron distribution in polycyclic aromatic systems, but it is not clear to the writer that the best compromise between simplicity and accuracy has yet been secured. 100... 

A large number of electron-rich polycyclic aromatic systems including anthracenes, azaanthracenes and larger homologues arenes undergo [4 - - 2]-cycloaddition with singlet... 

Significant through-space scalar couplings have been observed only in rare cases and in very close spatial proximity and usually 19F is involved in such couplings102-105, e.g., in the following fluorinated polycyclic aromatic systems ... 

Intercalation has been demonstrated with a number of other compounds having a polycyclic aromatic system and groups capable of forming hydrogen bonds. Among such compounds are the antibacterial 9-aminoacridine, the antimalarials mepacrine and chloroquine, the veterinary trypanocide ethidium (246), the thioxanthone lucanthone (247 R = Me) and its more active metabolite hycanthone (247 R = CH20H), which are used in the treatment of schistosomiasis, and the antineoplastic alkaloid ellipticine (248). A number of antibiotics, including the actinomycins, echinomycin and bleomycin, also intercalate. 

By studying stable ion chemistry of polycyclic aromatic systems, Laali et al.862 observed the ring closure of dicyanometacyclophanediene 254 with the involvement of diprotonated intermediate 255 [Eq. (5.318)]. When product 256 was treated again in superacids under different conditions, rearrangement took place to yield 1-cyanopyr-ene through mono- and diprotonated intermediates [Eq. (5.319)]. 

Quinones of the more reactive, polycyclic, aromatic systems can usually be obtained by direct oxidation, which is best carried out with chromium(vi) compounds under acidic conditions. In this way 1,4-naphthoquinone, 9,10-anthraquinone and 9,10-phenanthraquinone are prepared from naphthalene, anthracene and phenanthrene respectively (Expt 6.128). Also included in this section is the reduction of anthraquinone with tin and acid to give anthrone, probably by the sequence of steps formulated below. 

Arylboronic acids are readily available via transmetalation between ArSnMe3 and borane in THF. Consequently, a variety of arylpolyboronic acids is achievable from the stannanes previously synthesized by the SRN1 mechanism from ArCl or ArOH in around 80% yields [50, 51]. These arene di- and tri-boronic acids can be used as starting materials for the synthesis of polycyclic aromatic systems via double or triple Suzuki crosscoupling reactions [50, 51], as shown in Scheme 10.34 [51],... 

Various diaryIcarbenes, whose aryl groups belong to a polycyclic, aromatic system, react with a number of alkenes and form spirocyclopropanearenes. Such carbenes are generally prepared by thermal and photochemical decomposition of the corresponding diazo compounds. Other... 

Figure 13.10 Models for pyrone-type structures on polycyclic aromatic systems. (Reprinted from Ref. [37] with permission from Elsevier.)...

Unsubstituted heteroatom-bonded heteroatom Nitrogen and sulfur mustard Polycyclic aromatic systems (PAH)... 

Kalechits et al. (213) applied the sextet model to explain the different rates of hydrogenation over nickel and platinum of the polycyclic aromatic systems benzene, biphenyl, naphthalene, anthracene, phenan-threne, 1,2-benzanthracene, and pyrene. 

Alternative methods for preparing solvated alkali-metal graphites include either secondary solvation of the binary compounds or reduction of graphite by solutions of the alkali metal in electron-solvating media such as hexamethylphosphorus triamide (HMPT) or polycyclic aromatic systems in ethers , leading, e.g., to HMPT- or ether-solvated compounds. 

In one of the most interesting reports to appear during the year, Tazuke and Ozawa have provided the first example of the abiological photofixation of COa in the formation of 9,10-dihydrophenanthrene-9-carboxylic acid from irradiation of phenanthrene and carbon dioxide with an amine in dimethyl sulphoxide or dimethylformamide. Naphthalene and some other polycyclic aromatic systems also seem to react similarly. 

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