Electrochemical Oxidation of Abietic and Dehydroabietic Acids for Sustainable Access to C-7 and C-15 Oxygenated Abietanes.

Abietic and dehydroabietic acids are abundant diterpene constituents of gum rosin (colophony) and represent biorenewable feedstocks. While several oxidation strategies have been developed for their methyl ester derivatives, direct oxidation of the naturally occurring free carboxylic acids remains largely unexplored. In this study, we developed electrochemical protocols for the direct oxidation of abietanes at C-7, enabling the selective synthesis of ketones from naturally occurring abietic and dehydroabietic acids under sustainable conditions. The approach achieves benzylic oxidation of dehydroabietic acid and olefin oxidation of abietic acid, without the need for stoichiometric oxidants or prior esterification steps. The procedures are scalable, operating in both batch and flow electrochemical systems, and have been extended to complex mixtures such as colophony, highlighting their potential for direct valorization of gum rosin feedstocks. Moreover, a complementary mediated electrolysis strategy enables further oxygenation at C-15, expanding the scope of structural diversification.