Abstract
The aerobic oxidative cleavage of α-methylstyrene and other benzylic olefins catalyzed by N–hydroxyphthalimide (NHPI) under solvent-free conditions is described. The reaction was remarkably accelerated by the addition of azo-initiator (2,2′-azobis(2-methylpropionitryl)) or transition metal salts (Mn, Cu, Co) in combination with NHPI. Alkylammonium salts and acetophenone were successfully applied to increase the solubility of the polar NHPI catalyst in non-polar substrates. The effects of the catalyst and reaction parameters on the conversion of the substrate and the selectivity for ketones were investigated. New insights into the oxidation mechanism and NHPI-ammonium salt interaction are presented.
Highlights
The oxidative cleavage of C=C double bonds is of major importance in both the organic synthesis and industrial production of fine chemicals
The aerobic oxidative cleavage of a-methylstyrene and other benzylic olefins catalyzed by N–hydroxyphthalimide (NHPI) under solvent-free conditions is described
We have extended that study to gain a better understanding of this matter. 1H NMR spectroscopy revealed changes in the chemical shift of the proton in the NOH group in NHPI in the presence of ammonium salts
Summary
The oxidative cleavage of C=C double bonds is of major importance in both the organic synthesis and industrial production of fine chemicals. It represents an important transformation of alkenes to carbonyl compounds. Most of the reported oxidation procedures use toxic, hazardous and expensive reagents and produce large amounts of waste. The development of green methods for oxidative cleavage has received considerable attention. Progress has been made in this area through the application of oxygen as an environmentally friendly, cheap and readily available oxidant [4]. The aerobic oxidative cleavage of a-aryl-substituted alkenes has been successfully performed by photoirradiation or in the presence of metal- and organocatalysts
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