The Tsuji-Wacker oxidation oxidizes terminal olefin to the corresponding methyl ketone under the Wacker process condition. Almost identical to that of Wacker Process, the proposed catalytic cycle(Figure 1) begins with complexation of PdCl and two chloride anions to PdCl, which then undergoes subsequent ligand exchange of two chloride ligand for water and alkene to form Pd(Cl)(HO)(alkene) complex. A water molecule then attacks the olefin regioselectively through an outer sphere mechanism in a Markovnikov fashion, to form the more thermodynamically stable Pd(Cl)(OH)(-CH-CHOH-R) complex. Dissociation of a chloride ligand to the three coordinate palladium complex promotes β-hydride elimination, then subsequent 1,2-hydride migratory insertion generates Pd(Cl)(OH)(-CHOHR-CH) complex. This undergoes β-hydride elimination to release the ketone, and subsequent reductive elimination produces HCl, water, and palladium(0). Finally palladium(0) is reoxidized to PdCl with two equivalents of Cu(II)Cl, which in turn can be reoxidized by O.
The oxidation of terminal olefins generally provide the Markovnikov ketone product, however in cases where substrate favors the aldehyde (discussed below), different ligands can be used to enforce the Markovnikov regioselectivity. The use of sparteine as a ligand (Figure 2, A) favors nucleopalladation at the terminal carbon to minimize steric interaction between the palladium complex and substrate. The Quinox-ligated palladium catalyst is used to favor ketone formation when substrate contains a directing group (Figure 2, B). When such substrate bind to Pd(Quinox)(OOtBu), this complex is coordinately saturated which prevents the binding of the directing group, and results in formation of the Markovnikov product. The efficiency of this ligand is also attributed to its electronic property, where anionic TBHP prefers to bind trans to the oxazoline and olefin coordinate trans to the quinoline.