Copper acetate Wacker process

Hoechst-Uhde (2) A variation of the Wacker process, which makes vinyl acetate from ethylene and acetic acid. The catalyst is an aqueous solution of palladium and copper chlorides. 

Wacker (1) A general process for oxidizing aliphatic hydrocarbons to aldehydes or ketones by the use of oxygen, catalyzed by an aqueous solution of mixed palladium and copper chlorides. Ethylene is thus oxidized to acetaldehyde. If the reaction is conducted in acetic acid, the product is vinyl acetate. The process can be operated with the catalyst in solution, or with the catalyst deposited on a support such as activated caibon. There has been a considerable amount of fundamental research on the reaction mechanism, which is believed to proceed by alternate oxidation and reduction of the palladium ... 

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). 

Heating of the N,N-diarylamines with palladium(II) acetate in acetic acid at reflux results in smooth oxidative cyclization to the corresponding carbazole derivatives. A variety of substituents are tolerated in different positions. Thus, this procedure has found many applications in organic syntheses [30,55]. However, the drawback is that stoichiometric amounts of palladium(II) are required, as one equivalent of palla-dium(O) is formed in the final reductive elimination step. In the Wacker process, regeneration of the catalytically active palladium(II) species is achieved by oxidation of palladium(O) to palladium(II) with a copper(II) salt [57]. We were the first to demonstrate that oxidative regeneration of the catalytically active palladium(II)... 

Tri- and tetra-substituted dihydropyranones and furanones have also been synthesized by a Wacker/Mizoroki-Heck domino process (Scheme 8.72). Gouvemeur and cowoikers [151] very recently prepared these kinds of compounds using different palladium sources, copper acetate as redox mediator, oxygen as oxidant and lithium bromide as additive. The coupling of two electron-poor substrates, ethyl acrylate and -hydroxy alkynones 294, led to the desired compounds 295a-e in moderate yields. 

The oxidation of ethylene to acetaldehyde catalyzed by a combination of paUadium and copper is caUed the Wacker process (Equation 16.96). This process and related reactions that form vinyl acetate from ethylene, acetic acid, and oxygen were discovered and disclosed in the late 1950s and early The Wacker process remains the major indus-... 

In Wacker process, both palladium and copper ions shuttle between two oxidation states and act as the catalysts. A reaction similar to that of Wacker process, but between ethylene and acetic acid to give vinyl acetate, can also be effected by using palladium and copper catalysts. This is shown by reaction 8.2.1.5. 

Meanwhile, Wacker Chemie developed the palladium-copper-catalyzed oxidative hydration of ethylene to acetaldehyde. In 1965 BASF described a high-pressure process for the carbonylation of methanol to acetic acid using an iodide-promoted cobalt catalyst (/, 2), and then in 1968, Paulik and Roth of Monsanto Company announced the discovery of a low-pressure carbonylation of methanol using an iodide-promoted rhodium or iridium catalyst (J). In 1970 Monsanto started up a large plant based on the rhodium catalyst. 

---