Palladium catalyzed oxidation of renewable terpenes with molecular oxygen: oxidation of α-bisabolol under chloride-free nonacidic conditions

Abstract

A novel selective palladium catalyzed oxidation of α-bisabolol by molecular oxygen under chloride-free nonacidic conditions has been developed. α-Bisabolol is a sesquiterpenic alcohol available from essential oils of various plants. The reaction proceeds in aqueous methanol solutions over the Pd(OAc)₂/Cu(OAc)₂ catalytic system and gives exclusively the products resulting from the interaction of palladium with a sterically encumbered internal acyclic double bond. No concomitant oxidation of the second double bond, the endocyclic one, occurs. Novel poly-functionalized sesquiterpenoid compounds obtained at the oxidation of α-bisabolol are potentially interesting for cosmetic, fragrance and pharmaceutical applications.