36914-99-5Relevant academic research and scientific papers
Reactions of (η6-Arene)tricarbonylchromium Complexes: Hydrogenation, Nitration, and Bromination
Own
, p. 417 - 423 (2007/10/03)
In this study, we explore the reactions of coordinated arenes, e.g., hydrogenation, nitration, and bromination, to prepare compounds which are not accessible from conventional organic synthesis. The reaction products formed from reactions with the coordinated and the uncoordinated arenes are compared. The polycyclic aromatic hydrocarbons (PAHs) employed for this study include phenanthrene, methyl- and acetyl-phenanthrene, and benz[a]anthracene (BA). The tricarbonylchromium group demonstrated various characteristics which influence the reactions in this work, such as an electronic effect to deactivate hydrogenation, a steric effect to exhibit highly positional selective nitration, and a free radical mechanism to direct bromine to attack at the ring coordinated to tricarbonylchromium.
Cycloaromatization of α-oxoketene dithioacetals and β-oxodithioacetals with benzyl-,1-(naphthylmethyl) and 2-(naphthylmethyl)magnesium halides: Synthesis of condensed polynuclear aromatic hydrocarbons
Srinivasa Rao,Balu, Maliakel P.,Ila, Hiriyakkanavar,Junjappa, Hiriyakkanavar
, p. 3499 - 3510 (2007/10/02)
An efficient route for the synthesis of substituted naphthalenes, phenanthrenes and other polynuclear aromatic hydrocarbons has been developed. The methodology involves 1,2- (or sequential 1,4- and 1,2-) addition of either benzyl, 1-(naphthylmethyl) or 2-(naphthylmethyl) magnesium halides to α-oxoketene dithioacetals or β-oxodithioacetals followed by borontrifluoride etherate catalyzed cycloaromatization of the resulting carbinols.
Regioselective Catalytic Hydrogenation of Polycyclic Aromatic Hydrocarbons under Mild Conditions
Fu, Peter P.,Lee, Hong M.,Harvey, Ronald G.
, p. 2797 - 2803 (2007/10/02)
Hydrogenation of polynuclear hydrocarbons over a palladium catalyst at low pressure and ambient temperature affords regiospecifically the corresponding K-region dihydroarenes, while analogous reactions over a platinum catalyst take place regioselectively on terminal rings to provide the related tetrahydroarenes.Hydrogenation over palladium of phenanthrene, benzanthracene, 7,12-dimethylbenzanthracene, benzpyrene, 3-methylcholanthrene, dibenzanthracene, and chrysene gave 9,10-dihydrophenanthrene, 5,6-dihydrobenzanthracene, 5,6-dihydro-7,12-dimethylbenzanthracene, 4,5-dihydrobenzopyrene, 11,12-dihydro-3-methylcholanthrene, 5,6-dihydrodibenzanthracene, and 5,6-dihydrochrysene, respectively (Table I).Hydrogenation over platinum of benzanthracene, 7-methylbenzanthracene, 12-methylbenzanthracene, 7,12-dimethylbenzanthracene, benzopyrene, chrysene, dibenzanthracene, 5,6-dihydrobenzanthracene, 5,6-dihydro-7,12-dimethylbenzanthracene, and 4,5-dihydrobenzopyrene furnished the corresponding terminal ring tetrahydroarenes (Table II).Partial hydrogenation beyond the dihydro stage in the presence of palladium was exhibited only by hydrocarbons with more than one K region.In these cases, the second stage of hydrogen addition was generally slower than the first, so that the extent of reaction was readily controllable.Hydrogenation was blocked by alkyl substitution in an otherwise susceptible ring, and regioselectivity was diminished or abolished by increased hydrogen pressure, prolonged reaction, or acidity.The mechanism of reaction over palladium is proposed to involve concerted hydrogen addition to the K region, the region of minimum bond delocalization energy, preceded by localized ? and/or ? complexes.Evidence is presented that hydrogenations over platinum do not involve initial addition to the K region followed by isomerization into the terminal ring.Instead, these reactions are suggested to involve addition of 2 mol of hydrogen via an intermediate ? complex to the terminal ring which affords the most thermodynamically favored tetrahydroarene product, i.e., that which requires the minimum amount of energy for its formation.
