Organomercurial compounds

Addition of several organomercury compounds (methyl, aryl, and benzyl) to conjugated dienes in the presence of Pd(II) salts generates the ir-allylpalladium complex 422, which is subjected to further transformations. A secondary amine reacts to give the tertiary allylic amine 423 in a modest yield along with diene 424 and reduced product 425[382,383]. Even the unconjugated diene 426 is converted into the 7r-allyllic palladium complex 427 by the reaction of PhHgCI via the elimination and reverse readdition of H—Pd—Cl[383]. 

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]. 

With mercuric acetate (Hg(OOCCH2)2), olefins and / fZ-butyl hydroperoxide form organomercury-containing peroxides (66,100). The organomercury compound can be treated with bromine or a mild reducing agent, such as sodium borohydride, to remove the mercury. 

The reactivity of mercury salts is a fimction of both the solvent and the counterion in the mercury salt. Mercuric chloride, for example, is unreactive, and mercuric acetate is usually used. When higher reactivity is required, salts of electronegatively substituted carboxylic acids such as mercuric trifiuoroacetate can be used. Mercuric nitrate and mercuric perchlorate are also highly reactive. Soft anions reduce the reactivity of the Hg " son by coordination, which reduces the electrophilicity of the cation. The harder oxygen anions leave the mercuric ion in a more reactive state. Organomercury compounds have a number of valuable synthetic applications, and these will be discussed in Chapter 8 of Part B. 

Another major route to fluorinated organomercury compounds is thermal or photochemical decarboxylation offluonne-conlaining mercury carboxylates [/-Si, 169, 170,171, 172], as shown for example in equation 125 [153, 169] Via similar methodology, C6HjHgCF3 (60-75%) [171], (CF3)2Hg (92%) [/i59T, (02NCFCl)2Hg (58%) [172], and [(CF3)3C]2Hg (80%) [157] were synthesized, and several of these mercurials have been used as fluorocarbene precursors [166],... 

Larock, R C Organomercury Compounds in Organic Synthesis Springer-Verlag Berlin, 1985 Seyferth D Acc Chem Res 1972, 5 65... 

The reaction between an excess of Li and an organomercury compound is a useful alternative when isolation of the product is required, rather than its direct use in further synthetic work ... 

These reactions work best with X = I but the less-expensive RBr can be used in conjunction with a Zn-Cu alloy instead of pure Zn. Diaryls are best obtained from appropriate organoboranes or organomercury compounds ... 

An enormous number of organomercury compounds are known. They are predominantly of the same stoichiometries as those of Zn and Cd, viz. RHgX and HgR2, and may be prepared by the action of sodium amalgam on RX ... 

Interaction of the thiophene-containing organomercury compounds 272 (R = H, Me, Et) [74MI1, 79JCS(D)2037] with potassium tris(3-methylpyrazolyl) borate (KTp ) yields 273 [96JOM(515)213],... 

Abstraction of H+ from the protonated enol by water gives an organomercury compound. 

Organomercury compounds, reaction with NaBH4, 222 Organometallic compound, 345 polarity of, 143... 

Reviews of the use of organomercury compounds in organic synthesis have been published by Brilkina and Shushunov (1970), by Larock (1978, 1982, 1985), and by Wardell (1988). 

Organomercury compounds undergo a similar reaction. Alkyl and aryl Grignard reagents can be converted to carboxylic esters with Fe(CO)5 instead of CO. Amides have been prepared by the treatment of trialkyl or triarylboranes with CO and an imine, in the presence of catalytic amounts of cobalt carbonyl ... 

For a review of this and other free-radical reactions of organomercury compounds, see Barluenga, J. Yus, M. Chem. Rev., 1988, 88, 487. 

For a discussion of conversions of organomercury compounds to sulfur-containing compounds, see Larock, R.C. Ref. 300, p. 210. 

The reaction has not been elucidated. Presumably Michler s thioketone reacts with organomercury compounds to yield intensely colored, mesomer-stabilized diphenyl-methane derivatives. 

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