The Liquid-phase Oxidation of Hydrocarbons with Molecular Oxygen. II. A Highly Selective Formation of α-Tetralone by the Metal-catalyzed Oxidation of Tetralin in the Presence of N,N-Dialkylamides

Abstract The metal-ion catalyzed oxidation of tetralin was carried out in different solvents in which metal salts tend to be soluble. It was found that, for the production of α-tetralone, a chromium salt is the best catalyst among the first-transition-metal salts employed, while N,N-dialkylamides are the best solvents or the best additives. For example, in the tris(acetylacetonato)chromium(III)-catalyzed oxidation of tetralin in the presence of N,N-dimethylacetamide, α-tetralone was obtained in a 93.0% yield at a 27.2% tetralin conversion. The decomposition of α-tetralyl hydroperoxide (THP) with different first-transition-metal catalysts was also carried out in N,N-dimethylformamide in order to elucidate the formation mechanism for α-tetralone in the oxidation of tetralin in the presence of N,N-dialkylamides. It was concluded that the product distribution in the oxidation mainly depends on the decomposition mechanism of THP, and that N,N-dialkylamides seem to promote the reaction of the α-tetralylperoxyl radical with low valent metal ions, ROO·+Mn+→α-tetralone+OH−+M(n+1)+.