Oxidation of Dibenzyl Sulfide via an Oxygen Transfer from Palladium Nitrate

Dibenzyl sulfide was oxidized at the α-carbon to yield benzaldehyde in the presence of Pd(NO3)2. Oxygen itself could not oxidize the sulfide directly, instead the nitrato ligand of the palladium complex transferred oxygen to dibenzyl sulfide to form benzaldehyde. The X-ray crystal structure of the intermediate complex, cis[Pd(NO3)2{S(CH2C6H5)2}2], revealed that the nitrato ligand was unidentate. Para-substituted dibenzyl sulfides I, (YC6H4CH2)2S wherein Y = OCH3, CH3, Cl, CN, or NO2, were synthesized and reacted with palladium nitrate, and those with electron-donating substituents (Y = OCH3 and CH3) were good substrates for the oxidation reaction with palladium nitrate. Thus, the reaction mechanism of the oxygen transfer was proposed to include nucleophilic benzylic carbon.