Alkyl halides organomercury compounds

Ethers are prepared either by a Williamson synthesis or by alkoxymercuration/demercuration sequence. The Williamson ether sy thesis involves S -2 attack of an alkoxide ion on a primary alkyl halide. The alkoxymercuration reaction involves the formation of an intermediate organomercury compound, followed by NaBH4 reduction of the C-Hg bond. The net result is Markovnikov addition of an alcohol to an alkene. 

Historically, the first report of the Pd-catalyzed cross-conpling reaction with acyl halide used organomercury compounds. " Although alkyl- and arylmercnry chlorides did not work, the use of dialkyl- and diarylmercury componnds gave the desired ketones in good yields. Acyl bromides are necessary to bring about fruitful results. The use of HMPA as the solvent is also unavoidable (Scheme 9). 

Flankland synthesized organomercury compounds by the reaction of alkyl halides with sodium amalgam in 1852 [29]. 

Many other types of organometallics which are not acylated directly acid chlorides and which do not undergo addition to ketones may still transmetallate into the acylpalladiumfll) complex. Simple alkyl organomercurials have been acylated in this fashion to give moderate to good yields of ketones. " Larock has studied the palladium-catalyzed acylation of vinylmercury(II) compounds with acyl halides (equation 104). The reaction was only modestly productive and could not compare to the yield provided by aluminum chloride catalysis. 

Some organometallic compounds, for example, organomercury or organocobalt compounds, have very weak carbon-metal bonds, and are easily homolyzed to give carbon-centered radicals. Alkyl mercury hydrides are formed by reducing alkyl mercury halides, but they are unstable at room temperature because the Hg-H bond is very weak. Bonds to hydrogen never break to give radicals spontaneously because H" is too unstable to exist, but interaction with almost any radical removes the H atom and breaks the Hg-H bond (Scheme 4.9). 

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