Aerobic oxidation of 1-phenylethanol catalyzed by palladaheterocycles

Cyclometallated palladium compounds with pyridine were shown to serve as more efficient catalysts for the aerobic oxidation of 1-phenylethanol than a previously investigated analogue with an oxazoline ring. Substituents with different electronic properties in the phenyl ring were shown to exhibit an only minor influence on the reactivity of the catalytic system. The first step in the reaction consists of the splitting of the acetate bridge in the dimeric starting complex and coordination of a ligand to palladium. By ab initio calculations it was shown that, in the presence of solvent, a complex with pyridine was more stable than that with the alcohol, whereas the opposite situation was found in the gas phase. The complex with coordinated alcohol was stabilized by hydrogen bonding. Good agreement was found between the computed structure and the X-ray structure of the initial palladaheterocycle 1.