Co(II) Catalysed Oxidation of α-Pinene by Molecular Oxygen. Part 2

Epoxidation of α-pinene catalysed by tetrameric cobalt(III) complexes

“…Autoxidation of ␣-pinene with Co(OAc) 2 /NaBr in presence of acetic acid gave verbenone, myretenal and trans-verbenyl acetate as the main products [2] in 10, 20 and 29% selectivity, respectively. Air oxidation of ␣-pinene with Co(II) pyridine complexes under solvent-free conditions led to allylic oxidation products, while air oxidation by cobalt(II) halide, nitrate or acetate needed TBHP or glacial acetic acid as an activator [4,5]. Effect of solvent on the product distribution for the autoxidation of monoterpenes has also been reported [6].…”

“…Several reports on autoxidation of monoterpenes including ␣-pinene, ␤-pinene and limonene in presence of cobalt(II) salts have appeared recently [1][2][3][4][5][6]. Most of these studies use environmentally unacceptable bromide ion promoters and/or acetic acid media resulting in complex mixtures of oxygenated derivatives with very low selectivities.…”

Novel access to verbenone via ruthenium nanoparticles-catalyzed oxidation of α-pinene in neat water

“…t-BHP (Entry 4), an optimum verbenone yield of 37 % was achieved. In other cases (Entries 5-6), the lower amount of the ketone could be attributed to the formation of higher amounts of by-products, such as the ones resulting from skeletal rearrangement of -pinene derivatives under the reaction conditions [21,47]. Hydrogen peroxide was tested under our conditions for comparison.…”

Autoxidation of Cycloalkenes by the System “Molecular Oxygen-bis(acetylacetonato) Cobalt (II) Complex-butyraldehyde”

“…8,[22][23] For example, in the presence of isobutyraldehyde the epoxidation of cyclohexene catalyzed by bis-2-acetoacetoxy-ethylmethacrylate copper for 24 h affords epoxycyclohexane with 99% selectivity and 84% conversion. 8 On the other hand, epoxidation of alkenes in the presence of cobalt complexes has attracted much less attention, [24][25][26][27][28][29] and the reported studies mainly focus on the oxidation of monoterpenes catalyzed by cobalt halides 24,28 or a silica-supported cobalt complex. 25 In those catalytic systems, the defects of low conversion and selectivity still exists.…”