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

Abstract

Aqueous suspensions of Ru(0) nanoparticles, stabilized with hydroxyethylammonium salts and possessing sizes around 2 nm, proved to be active and selective in the mild oxidation of α-pinene in the presence of tert-butylhydroperoxide, in neat water. Verbenone, a product of great interest for fine chemistry, was obtained as major product with yield up to 41% under optimized conditions. 2-hydroxy-3-pinanone was identified as a co-product of the reaction, but with very low amount (<7%). Kinetic investigations allowed determining the potential reaction intermediates and by-products. Moreover, mechanistic studies with radical scavengers confirmed that α-pinene oxidation mainly implies both carbon- and oxygen-centered radicals.