Polyaromatic compounds, reaction with

Polyaromatic compounds, reaction with dimsyl anion 607... 

Since diazaquinones are among the most powerful dienophiles, they undergo [4+2] cycloaddition (Diels-Alder) reactions with a great variety of dienes to give various heterocyclic systems accessible with difficulty by other methods. Diazaquinone reacts with butadiene and substituted butadienes, carbocyclic and heterocyclic dienes, 1-vinylcycloalkenes, polyaromatic compounds and vinylaromatic compounds to afford bicyclic and polycyclic bridgehead diaza systems, including diazasteroids (Scheme 56). 

An interesting reaction of dimsyl anion 88 is the methylation of polyaromatic compounds. Thus naphthalene, anthracene, phenanthrene, acridine, quinoline, isoquinoline and phenanthridine were regiospecifically methylated upon treatment with potassium t-butoxide and DMSO in digyme or with sodium hydride in DMSO123-125. Since ca. 50% of D was found to remain in the monomethyl derivative 93 derived from 9-deuteriophenanthrene 92, the mechanistic route shown in Scheme 2 was suggested125. 

The kinetics associated with catalytic reactions are complex however, some general trends can be determined. Reactions are often first order with respect to the reactant, and the rates of hydrodechlorination are faster than hydrogenation. Polyaromatic compounds react faster than monoaromatic compounds, and chlorinated alkenes react faster than their corresponding alkanes. Finally, the reaction rate often increases with increasing degree of chlorination, though this does not hold true for the chlorinated ethylenes. 

The rates of hds of thiophen, benzothiophen, and polyaromatic thiophens were compared over a sulphided commercial C0O-M0O3/AI2O3 catalyst (573 K, 71 atm). Pseudo-first-order kinetics were obeyed. The mechanism of the reaction with thiophen (involving ring hydrogenation) was different from that of other compounds (S extmsion). The reactivity was not governed solely by the size of the ring compound interaction of the ir-electron system with the catalyst surface may be more important than the interaction of S except for thiophen. 

Electron-rich polyaromatic compounds such as anthracene, pyrene, and pery-lene [107] are suitable as photosensitizers as they give redox reactions with DPI salts through exciplex to finally yield the initiating species for photoinduced cationic polymerizations. Scheme 11.28 demonstrates the mechanism of a polymerization followed via exciplex formation through the excited sensitizer with the ground-state onium salt. 

Likewise, Orr et al.29,30 have explored the possible use of tyre pyrolysis oil as a solvent for coal liquefaction. The potential of this alternative was demonstrated by the fact that coal-TPO mixtures were transformed with higher conversion than when coal was reacted directly with ground waste rubber tyres. It is proposed that the polyaromatic compounds present in the TPO favour coal dissolution during liquefaction. Treatment of coal-TPO mixtures (50/50%) at 430 °C under 68 atm of cold-hydrogen pressure in the presence of a Mo catalyst led to a high coal conversion in just 10 min of reaction. From electron probe microanalysis of the coal particles after the reaction, the authors conclude that TPO favours the catalyst dispersion and its contact with coal, which results in enhanced coal conversion. 

Fused ring systems have been synthesized using both inter- and intra-molecular Wittig reactions. Various polyaromatic compounds, e.g., (169), have been prepared in one step by the reaction of the diylide (168) with the appropriate o-quinone. An intramolecular reaction of ylide (170) has been used to synthesize the dihydronaphthacene (171) as an early step in the synthesis of 3-demethoxyaranciamycinone, an anthracyclinone analogue. ... 

The electrochemical reactions which produce polyaromatic compounds from the monomer have stoichiometries in the range of 2-2.5 Faraday/mole of monomer. The stoichiometry for the formation of the polymer chain is 2 for large chain lengths, plus the charge associated with reversible oxidation of the polymer (0 to 0.5). The latter quantity varies with the individual monomer system, with the anion which is inserted upon oxidation of the polymer, and with the solvent and other components of the electrolyte medium. Anion content and degree of oxidation of various polymer films is presented in Table 2.2. 

Reaction with Organolithium Reagents. The fluorination of vinyl lithium derivatives with NFSi has been demonstrated in good yields with complete retention of configuration about the double bond. Phenyl lithium reacts rather poorly with 7V-fluorobenzenesulfonlmlde, but more complex phenyl lithium derivatives have been fluorinated to prepare fluoro- and polyfluoro-veratraldehydes as well as complex fluorinated polyaromatic compounds. Organolithium derivatives of heterocycles have been fluorinated by reaction with NFSi at low temperature. In this manner, fluoro-pyrroles and 2-fluoro-5-methylthleno[3,2-b]pyrldlne are prepared from their corresponding llthlo-parent compounds (eq 16). ... 

A large number of substituted polyaromatic and heteroaromatic compounds are also accessible through 5-BuLi-induced ortho lithiation reactions. These include, for example, derivatives of naphthalene, furan, thiophene, pyridine, quinoUne, and N-protected imidazoles. The smooth ortho lithiation of pyridyl (eq 25) and quinolinyl systems is notable given the weU-known tendency of organolithium compounds to undergo nucleophilic addition reactions with the pyridine nucleus. ... 

Luminescence is applicable to polyaromatic compounds, fluorescent dyes, fluorimetric reaction products, polychlorinated biphenyls (PCBs), phe nols, 50% of pesticides, many semivolatiles, many nonvolatiles, and petroleum oils. For luminescence to work, the compound must fluoresce. However, many large molecules absorb but do not fluoresce in the visible or UV. For such non-fluorescing compounds, absorption spectroscopy must be used instead (with much less sensitivity) or, alternatively, the organics can sometimes be complexed. 

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