Computational Study on the Palladium-Catalyzed Allenylative Dearomatization Reaction

The detailed mechanism of the Pd-catalyzed coupling of naphthalene allyl chloride with allenyltributylstannane, resulting in the dearomatization of the naphthalene group, has been studied using density functional theory (DFT) calculations at the B3LYP level. The catalyst cycle can be divided into three main stages involving oxidative addition, transmetalation, and reductive elimination, none of which contains significantly large barriers. It is found that the oxidative addition takes place through a monophosphine pathway. The transmetalation step is responsible for the formation of the propargylic dearomatized product, due to the orientation of the metal-coordinated allenyl ligand. Reductive elimination of the dearomatized product from the intermediate (η3-allylnaphthalene)­(η1-allenyl)­PdPH3 occurs by coupling of the terminal carbon of the η1-allenyl ligand with the ortho carbon of the η3-naphthalene ligand. Furthermore, it is shown that dichloromethane as solvent does not change the mechanistic picture significantly.