Catalysis transition metal-catalyzed alcohol oxidation

The elimination of a hydrogen atom positioned on a carbon to the central metal constimtes an important reaction in transition metal catalysis. In the classical example, an alkylmetal intermediate is reversibly converted to an alkene and a metaUiydride (scheme 1.12). Despite the fact, that the resulting hydridometal complex can be exploited in various catalytic processes including polymerization reactions, [57] cycloisomerizations, [58] annulations, [59] etc., the ]S-hydride elimination is often considered undesired in transition metal catalyzed cross couplings. Thus, efforts have often been concentrated towards the prohibition of this fundamental reaction [60]. Nevertheless, the ]S-hydride elimination is a vital transformation in a number of catalytic processes including the ene-yne coupling reported by Trost [61] and Skrydstrup, [62] oxidation of alcohols, [63] the Heck reaction etc [64]. 

The epoxidation of enones using chiral phase transfer catalysis (PTC) is an emerging technology that does not use transition metal catalysts. Lygo and To described the use of anthracenylmethyl derivatives of a cinchona alkaloid that are capable of catalyzing the epoxidation of enones with remarkable levels of asymmetric control and a one pot method for oxidation of the aUyl alcohol directly into... 

Hydrogenation of Carbon Monoxide or Carbon Dioxide. There are two important aspects of metal carbides in CO-H2 reactions including methana-tion, Fischer-Tropsch synthesis, alcohol synthesis, and water gas shift reaction. First, metal carbides, by themselves or together with other phases, are considered as active phases in these reactions catalyzed by Fe, Co, and Ni. These carbide phases are formed in situ from the respective metals or oxides during the reaction. This aspect is not discussed here. Instead, catalysis by early transition metals intentionally prepared in a stable carbide form is the subject of this section. Molybdenum and tungsten carbides are by far the most extensively studied. 

Metal oxides are widely used as catalyst supports. For instance, a-Al203 is employed as a support for catalysts in the partial oxidation of ethylene to ethylene oxide, because a non-reactive material is essential for such applications [141]. However, aluminas are also important catalysts in their own right. Transition aluminas are known to catalyze the isomerization of alkenes, the dehydration of alcohols, H/D exchange reactions and C—H bond activation [142]. Consequently, the development of an understanding of both their bulk and their surface structure has been a key goal in catalysis, with solid-state NMR being widely employed to this end. 

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