Base-Catalyzed Hydrogenation: Reduction of Polycyclic Aromatic Compounds

摘要

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℃. 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℃. 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.