Base-Catalyzed Hydrogenation:  Reduction of Polycyclic Aromatic Compounds

Abstract

Dihydrogen can be activated by lithium and potassium organoamides, particularly the diisopropyl and bis(trimethylsilyl) derivatives, to reduce aromatic compounds at 1000 psig and 200 °C. Naphthalene was hydrogenated to tetralin in 100% yield by both reagents; anthracene was reduced with the bis(trimethylsilyl)amide catalyst to a mixture of the corresponding monocyclic aromatic derivatives, 1,2,3,4,4a,9,10,10a-octahydroanthracene (15%) and 1,2,3,4,5,6,7,8-octahydroanthracene (84%); phenanthrene was reduced with this base to a mixture of 1,2,3,4,5,6,7,8-octahydrophenanthrene (63%), 1,2,3,4,4a,9,10,10a-octahydrophenanthrene (33%), and 1,2,3,4-tetrahydrophenanthrene (4%); chrysene was converted by the same reagent to 1,2,2a,3,4,5,6, 6a,9,10,11,12-dodecahydrochrysene (70%) and 1,2,2a,3,4,5,6,6a-octahydrochrysene (25%); and 1,2-benzanthracene was hydrogenated to a mixture of dihydro- and dodecahydro-1,2-benzanthracenes. The reaction products show a striking selectivity for the preservation of an interior benzene ring. The catalytic properties of the strong bases depend on the nature of the organic ligands in the dialkylamide and the corresponding metal cations. The reactions proceed at modest pressures, about 500 psig, but require high temperatures, about 200 °C. The products of the reaction with dideuterium were investigated by magnetic resonance spectroscopy to define the reaction pathway. The results of these experiments and other available information suggest that hydrogen is transferred from an anionic dihydrogen−dialkylamide complex to the aromatic compound in the slow step of the reaction.

Hydrogenation of Condensed Aromatic Compounds over Mesoporous Bifunctional Catalysts Following a Diels–Alder Adduct Pathway

“…In contrast, substitution of one of the external rings with a functional group (at least a methyl group) makes this ring unattractive for coordination to the metal center, and hence resistant to hydrogenation. Very close conclusions with regard to the selectivity for the preservation of an interior benzene ring were drawn with hydrogen activated by lithium and potassium organoamides, in which the catalytic properties of the strong bases depend on the nature of the organic ligands in the dialkylamide and the corresponding metal cations . Other studies in which active carbon afforded hydrogen transfer using molecular hydrogen indicated that it is possible to change the reaction pathway to provide the hydrogenation of the central ring to a high extent …”

“…Very close conclusions with regard to the selectivity for the preservation of an interior benzene ring were drawn with hydrogen activated by lithium and potassium organoamides, in which the catalytic propertieso ft he strong bases depend on the nature of the organicl igands in the dialkylamide and the corresponding metal cations. [10] Other studies in which active carbon afforded hydrogen transfer using molecular hydrogen indicated that it is possible to change the reaction pathway to provide the hydrogenation of the central ring to ahigh extent. [11] The effect of the hydrogen source has also been demonstrated by several authors.…”

Hydrous Pyrolysis of Polycyclic Aromatic Hydrocarbons and Implications for the Origin of PAH in Hydrothermal Petroleum

“…However, several observations strongly suggest that the dark, flaky material derived exclusively from formic acid, including: (1) the lack of this material in experiments without formic acid, (2) the absence of any aromatic character, (3) the absence of other cracking products, and (4) essentially all of the starting PAH could be accounted for among the products. In addition, char formation has not been reported by other researchers who examined the pyrolysis of phenanthrene and anthracene. − Both the carbonaceous material and minerals represent potential sinks for carbon from formic acid.…”

“…First, we sought to examine the thermal stability and reactivity of PAH in hydrothermal environments. Previous hydrous pyrolysis studies have found phenanthrene to be unreactive in water at high temperatures when heated alone or in the presence of inorganic salts, CaCO 3 , or montmorillonite. , However, other studies have shown that phenanthrene as well as anthracene may be extensively hydrogenated in the presence of H 2 or other hydrogen donors. − These results suggest the possibility that PAH may be partially hydrogenated within H 2 -rich hydrothermal systems, but hydrogenation has only been reported for anhydrous conditions with the PAH dissolved in organic solvents, and the effect of water on hydrogenation reactions remained uncertain. With increasing temperature, the dielectric constant of water decreases and the solvent properties of water more closely resemble those of organic solvents.…”

“Broken-hearted” carbon bowl via electron shuttle reaction: energetics and electron coupling

“…31 Indeed, as presented in this report, release of strain energy can be the driving force for planarization of the naturally curved buckybowl surface (e.g., C 20 H 10 , corannulene), since there is no direct route to cleave a C]C bond, except through uncontrollable ash vacuum pyrolysis 22,27,29 or addition of a directing group (and a catalyst). 32 Although there are numerous reports of catalytic hydrocracking of planar polycyclic aromatic hydrocarbons (PAHs) i.e., increasing the ratio of hydrogen-to-carbon, [33][34][35][36] there are very few accounts on C-C bond cleavage following the hydrogenation step. 37 The literature precedent for C-C bond scission primarily relies on the assistance of transition metal catalysts, high hydrogen pressure, elevated temperatures, or a combination of all three parameters.…”