Catalyzing reactions, oxygen species capable

Scheme 75. Various oxygen species capable of catalyzing reactions.

In fact, the role of copper and oxygen in the Wacker Process is certainly more complicated than indicated in equations (151) and (152) and in Scheme 10, and could be similar to that previously discussed for the rhodium/copper-catalyzed ketonization of terminal alkenes. Hosokawa and coworkers have recently studied the Wacker-type asymmetric intramolecular oxidative cyclization of irons-2-(2-butenyl)phenol (132) by 02 in the presence of (+)-(3,2,10-i -pinene)palladium(II) acetate (133) and Cu(OAc)2 (equation 156).413 It has been shown that the chiral pinanyl ligand is retained by palladium throughout the reaction, and therefore it is suggested that the active catalyst consists of copper and palladium linked by an acetate bridge. The role of copper would be to act as an oxygen carrier capable of rapidly reoxidizing palladium hydride into a hydroperoxide species (equation 157).413 Such a process is also likely to occur in the palladium-catalyzed acetoxylation of alkenes (see Section 61.3.4.3). 

The reaction is comparatively slow. However, it was noticed that copper(II) greatly accelerates the reaction rate with GSH (Figure 22.2). The reduction of Cu + ions by GSH could give rise to the formation of a redox-active species capable of catalyzing the subsequent reduction of molecular oxygen into superoxide anion, and that of hydrogen... 

This work shows that oxygen-free sulfite in lime/limestone slurries, exposed to sulfur dioxide, slowly decomposes under process conditions. In fact, auto-redox reactions of sulfur oxyacids can occur in all coal desulfurization systems, including coal-gasification systems and impurities present in commercial flue gas systems are capable of catalyzing the reaction under process conditions. Our experiments indicate that any large-scale coal utilization will depend on appropriate control of the autoredox reactions of sulfur species. 

Olefin oxidations can also be accomplished by the palladium nitro complex [(MeCN)2PdCl(N02)] (45), which has the capability to act at the same time as an oxygen atom transfer agent and olefin activator [116, 119-121]. Stoichiometric reaction of 45 and 1-decene under nitrogen atmosphere revealed the formation of palladium nitrosyl species identified as [PdCl(NO)] . At 60°C in air, the toluene solution of 45 catalyzed the oxidation of 1-decene to 2-decanone with a TON of 4. The same reaction carried out at room temperature afforded within 24 h a TON of 2. 

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