Diarylmercury compounds

We return now to the mercuro-de-diazoniation. Nesmeyanov s school continued the work on metallo-de-diazoniations from 1929 to 1953 (see summary by Nesmeyanov, 1972). A major discovery was made at the very beginning, namely the influence of copper powder (Nesmeyanov, 1929 b Nesmeyanov and Kahn, 1929). With this addition metallic mercury was not required instead the double salt of the diazonium chloride and mercuric chloride was used. The copper reacts stoichiometrically as an electron donor. Therefore, either arylmercuric chlorides (Scheme 10-87) or diarylmercury compounds (Scheme 10-88) can be obtained. These reactions are called Nesmeyanov reactions. Specific examples are the syntheses of di-2-naphthyl-... 

Diarylhydrazines, from ArNJ 195 Diarylmercury compounds 273 f. 1,4-Diazabicyclo [2.2.2]octane (DABCO) 360 Diazenes 6, 126, 192, 195, 211, see also Azo compounds... 

Protodemercuration was first studied kinetically by Kharasch et al.604, who measured, qualitatively, the rates of cleavage of diarylmercury compounds by acids, viz. 

Similarly, dilithiation of 2-(4-bromophenoxy(ethanol in the presence of magnesium 2-ethoxyethoxide followed by reaction with 0.5 equiv. of HgCl2 afforded the corresponding diarylmercury compound 4-(H0(CH2)20)-C6H4)2Hg 26 whose crystal structure has been determined (Equation (12)).47 In addition to these alcohol and ether derivatives, thio- and phosphinoaryl mercury compounds have also been prepared. Thus, the dilithium salt... 

A well-known reaction in organomercury chemistry consists of the conversion of arylmercuric chlorides to diarylmercury compounds by means of solutions of sodium iodide or sodium thiosulfate. Treatment of chloromercuriferrocene readily produces diferrocenylmercury (XXIX) under these conditions (63, 90). 

The dialkyl- and diarylmercury compounds are very useful for the preparation of other organo compounds by reactions of the general type ... 

Although there are numerous examples of dimerizations of organo-metallic reagents by copper(II) salts, one particularly interesting example concerns 2,2 -dilithiobiphenyl 304). Wittig and Klar have proposed several transient copper(II) ate complexes and a stable copper(I) complex to account for the high yields of biphenylene and o-tetraphenyl-ene. Diarylcopper(II) compounds were supposedly isolated, and characterized by elemental analysis, from diarylmercury compounds and copper at 120°C 11, 197) an unlikely reaction. 

Aromatic boranes are synthesized from diborane and arylmagnesium halides [i 5], arylmercury halides [iS5], or diarylmercury compounds [/S i]. Their oxidation furnishes phenols in variable yields. A large excess (up to 16 mol) of BH3 is necessary for high yields (equations 604 and 605). 

Diarylmercury compounds can also be obtained by reduction of the aryl-mercuric halides or other salts obtained as above. This reduction can be effected by means of hydrazine hydrate,172 sodium stannite,173-175 magnesium,176 or copper in pyridine177 or electrolytically, e.g. ... 

Historically, the first report of the Pd-catalyzed cross-coupling reaction with acyl halide used organomercury compounds. Although alkyl- and arylmercury chlorides did not work, the use of dialkyl- and diarylmercury compounds 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). 

The use of tributyltin methoxide seems to be specific to reactions of isopropenyl acetate, giving a method for the a-arylation of acetone. Aryl-acetones have also been prepared by the copper-catalysed arylation of acetylacetone in di-methylformamide at elevated temperatures. p-Keto-esters may also be arylated with the aryl-lead reagents that are prepared in situ from diarylmercury compounds and lead tetra-acetate. ... 

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