Organomercury compounds, transmetallation

Pd(II) salts promote the carbonylation of organomercury compounds. Reaction of phenylmercury chloride and PdCh under CO pressure affords benzophenone (429)[387]. Both esters and ketones are obtained by the carbonylation of furylmercury(Il) chloride in alcohol[388]. Although the yields are not satisfactory, esters are obtained by the carbonylation of aryl- and alkylmercuryfll) chlorides[389,390]. One-pot catalytic carbonylation of thiophene, furan, and pyrrole (430) takes place at the 2-position via mercuration and transmetallation by the use of PdCb, Hg(N03), and CuCl2[391]. 

In 1864, Frankland discovered the transmetallation reaction between diorganomercurials and zinc metal (equation 9). It is generally applicable when the organomercury compounds are available and when it is necessary to prepare absolute salt free diorganozinc compounds. 

Transmetallation of organomercury compounds with palladium salts proceeds smoothly to give highly reactive organopalladium compounds which readily react with olefins19 ... 

Alkyl and vinylthallium(in) compounds are mostly obtained by oxythallation of alkenes or alkynes. They can also be formed by transmetallation between, for example, an organomercury compound and thallium(ni) salts. Various types of reactivity have been observed for these compounds. The evolution of the carbon-thallium bond into functionalised products usually takes place homolytically or heterolytically. The ligand coupling process has also been evoked to rationalize a small number of transformations. 

Transmetallation of a suitable organomercury compound is a useful means of preparing pure Grignard reagents (equation 18.15), and transmetallation 18.16 can be used to synthesize compounds of type R2Mg. 

Organomercury compounds are widely used for syntheses of organometallic compounds by the transmetalation or metathesis reaction similar to organozinc compounds. For example, organozinc compounds and organomagnesium compounds (1866) are prepared by the transmetalation of organomercury compounds with a metal [30,31]. 

An alkenylplatinum complex, 180, which is able to support a Geo radical as the cr-bonded ligand, has been prepared by transmetallation using an organomercury compound.The complex with carbomethoxy and hydroxy ligands trans disposed 181 has been obtained and characterized. 

Scheme 10 Transmetalation of an organomercury compound with alkaline-earth metals yielding the corresponding pentafluorophenyl complexes...

However, cycloauration is, sometimes, difficult to achieve with direct activation of a C—H bond and transmetallation reaction of organomercury or organotin compounds with the appropriate gold compounds is, hence, frequently used. This procedure has been used with azobenzene, 36 A, A -dimethylbenzilamine,1937,1938 4,4 -dimethyl-2-phenyl-l, 3-oxaazoline,1938 1 - (dii zene,... 

A general method for the synthesis of organomercurials is the transmetallation of mercury(n) salts with other organometalhc species. Organohthium and -magnesium compounds continue to be widely employed for the preparation of complexes with formula RHgX or HgR2 (see equation 1). 

Organolanthanide chemistry is dominated by the trivalent compounds. " Compounds in oxidation state (II) are restricted to derivatives of europium, samarium, and ytterbium, but they have considerable importance in both organic and organometallic syntheses because of their reducing properties. " Redox transmetalation reactions of organomercurials with lanthanide metals provide convenient syntheses of a number of diorganolanthanides, for example, R2M, R = CgFj or PhCC, M = Yb or Eu. " °... 

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. 

The regioselective syn, vicinal lithiation of cyclopropane and cubane amides has been reported. Transmetalation to organomercury or zinc compounds facilitates functionalization, as shown in Scheme 43. 

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