Oxidation of Dibenzyl Sulfide via an Oxygen Transfer from Palladium Nitrate

摘要

Dibenzyl sulfide was oxidized at the メ-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.