Mechanism and chemoselectivity of the Pd(II)-catalyzed allylation of aldehydes: A density functional theory study

(Chemical Equation Presented) Density functional theory calculations at the PBE1PBE/DGDZVP level of theory were performed to investigate the mechanism and chemoselectivity of Pd(II)-catalyzed allylation of aldehydes. The transfer of formaldehyde to the π-allyl group of bis-π-allylpalladium complex is a thermodynamically favored process (ΔG = -1.4 kcal/mol), and its Gibbs free energy of activation (ΔG^‡) corresponds to 23.0 kcal/ mol. Further support for the mechanism proposed herein, which requires the coordination of an aldehyde molecule to the metal center, comes from correctly predicting the chemoselectivity of the reaction when it is conducted with mixed bis-π-allylpalladium complexes containing crotyl, methallyl, and 2-methoxyallyl groups.