Palladium-Catalyzed Acetoxylation of γ-Dehydro-aryl-himachalene: The Synthesis of a Novel Allylic Acetoxylated Sesquiterpene and a π-Allyl Palladium(II) Complex.

Allylic oxygenated derivatives of himachalenes are highly valued molecules due to their potential applications in perfumery, cosmetics, and pharmaceuticals. Previous attempts at catalyzed allylic oxidation of himachalenes led to the formation of a very stable η(3)-allyl palladium complex, preventing any further reaction development. Herein, we present the first successful palladium-catalyzed synthesis of a novel allylic acetoxylated derivative of himachalenes. This reaction was achieved by incorporating an aromatic ring into the substrate structure. The resulting intermediate complex was isolated and characterized using nuclear magnetic resonance spectroscopy and X-ray crystallography. Density functional theory (DFT) calculations were performed to compare the reactivity of the newly synthesized complex with previously reported ones. The theoretical results confirm that the introduction of an aromatic ring enhances the reactivity of the η³-allyl palladium complex, thereby facilitating the desired transformation.