Hydrogenation organoalkalis

Base catalysis is most effective with alkali metals dispersed on solid supports or, in the homogeneous form, as aldoxides, amides, and so on. Small amounts of promoters form organoalkali comnpounds that really contribute the catalytic power. Basic ion exchange resins also are usebil. Base-catalyzed processes include isomerization and oligomerization of olefins, reactions of olefins with aromatics, and hydrogenation of polynuclear aromatics. 

All unsaturated hydrocarbons that possess removable allylic hydrogens or activated double bonds readily undergo oligomerization in the presence of basic reagents.30,31 Alkali metals, organoalkali compounds, and alkali alcoholates are most frequently applied. 

There are three general types of metallation reactions (metal-hydrogen exchange) that are commonly used to synthesize organoalkali metal compoimds from organic molecules Direct reaction with an alkali metal, reaction with an alkali metal hydride, or reaction with an organo- or amido-alkali metal. Since these reactions involve acid/base equilibria, they are dependent on both the C-H acidity of the organic molecule and the basicity of the alkali metal source. 

The direct reaction of an organic molecule with an alkali metal produces an organoalkali metal compound and hydrogen gas (equation 5). 

Halogen/metal permutation and hydrogen/metal permutation (usually apostrophed as "metalation") dominate the interconversion methods. They employ organoalkali reagents such as phenyllithium, methyllithium, -butyllithium, iec-butyllithium, or the superbasic LIC-KOR mixture. However, even if commercial, these reagents have to be made beforehand. The reaction of a chloro- or bromo-substituted hydrocarbon with lithium, sodium, or magnesium offers a standard entry to them. Thus, ultimately one always has to revert to the metal. 

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