Pd (Ⅱ) Wacker-type Oxidation Catalytic Oxygen Oxidation Reaction Studies

The palladium(II)-catalyzed oxidation of terminal olefins to methyl ketones, known as the Wacker oxidation (or Tsuji-Wacker oxidation), is one of the most important reactions which has extensive synthetic applications in laboratories and factories. Classically, the reaction is conducted with catalytic PdC12and stioichiometric CuCl under aerobic. atmosphere. Palladium decomposition, olefin isomerization, chlorinated byproducts, and copper waste have been recognized as considerable limitations for oxidation. To address these limitations, many ligands of palladium have been developed, and many oxidants, such as nitrous oxide, H2O2,1,4-benzoquinone (BQ), pressured oxygen, and tert-butylhydroperoxide (TBHP), have been used. These modified methods undoubtedly widen the range of application of the Tsuji-Wacker oxidation. However, they also increase cost of the oxidation and demand higher practical operation skills for the oxidation. Therefore, it is still highly desirable to develop a facile and efficient Wacker-type oxidation that does not rely on the ligand and uses ambient-pressure oxygen as the sole oxidant.In general, molecular oxygen can be applied for the Tsuji-Wacker oxidation of alkyl-substituted terminal olefins, while stronger oxidant, such as TBHP, is required for such oxidation of stryenes. Herein, we reported an efficient and economical palladium-catalyzed oxidation system. The oxidation system, charactered by adding not ligand and using molecular oxygen as the sole oxidant, can realize the Tsuji-Wacker oxidation of terminal olefins and especially styrenes to methyl ketones; in addition this system can achieve tandem Wacker oxidation-dehydrogenation of terminal olefins to α,β-unsaturated ketones.