Aromatics mercury salts

Reduction of benzophenones with FeCl2/NaB(Et)3H63 or LiAlH464 or with NaBH4/CH3S03H65 gives bis-phenylmethanes in low yields. Alternatively, bidentate or monodentate aromatic mercury salts reduce thioketones to diarylmethanes.66... 

The use of mercury has the merit of easy preparation of the aryl mercury compounds directly from the aromatic compound and an inorganic mercury salt, sometimes in complete regioselective manner. Preparation of the other metallated species generally involves more synthetic steps. An example of a radiofluorode-mercuration reaction (Scheme 29) is the synthesis of 6-p F]fluorometaraminol... 

WOLFFENSTEIN-BOTERS REACTION. Simultaneous oxidation and nitration of aromatic compounds to nitrophcnols with nitric acid or the higher oxides of nitrogen in the presence of a mercury salt as catalyst. Hydroxynitration of benzene yields picric acid. 

The mechanism of mercuration is shown in Scheme 2. In the first step, the mercury salt forms a Jt-complex with the aromatic substrate [15, 16]. In 1982, Lau, Huffman, and Kochi [17] reported the first isolation and full characterization (including X-ray molecular and crystal structure) of such an intermediate, a complex of hexamethylbenzene with Hg(TFA)2. The X-ray structure revealed a Hg2( -TFA)i framework with a molecule of C6Me6 -coordinated to each of the Hg atoms. Analogous Jt-complexes have also been observed and studied by Dean and co-workers [18] and more recently by Barron s [19] and Gabbai s [20] groups. The Jt-complex intermediate can rearrange to the ej-complcx (a Wheland intermediate) directly, or sometimes via electron transfer, to produce a radical ion pair which then collapses (Scheme 2) [21,22]. 

It is rather important to note that if an aromatic nitro compound is the substance being nitrated, addition of mercuric nitrate to the nitric acid has no effect on the reaction. For example, nitrobenzene is nitrated to dinitrobezene in the same yield both in the presence of a mercury salt and in its absence. This can be explained by the fact that nitro compounds such as nitrobenzene do not yield addition product with mercuric salts. 

Among different metal salts catalysing the nitration of aromatic systems, mercury salts occupy an exceptional position (perhaps tallium would also play a certain part, see p. 27). 

Arylmercuric salts can be obtained with extraordinary ease by mercuration of aromatic compounds with mercury salts, the reaction involving direct replacement of hydrogen by mercury ... 

Further reports on the preparation of phospholes, e.g. (113), by the addition of phosphines to diacetylenes have appeared. Braye and coworkers found that the reaction was best catalysed by concentrated potassium hydroxide or by means of cuprous or mercury salts. Contrary to previous reports the free radical reaction, catalysed by AIBN, also gave good yields. A full account has now been produced of the low inversion barrier of phospholes (114). The energy barriers to inversion of phos-phindoles (115) and dibenzophospholes (116) are significantly higher, results interpreted in terms of disruption of stabilization due to phosphole aromaticity in the planar transition state. The site of protonation of... 

Nucleosides are formed from benzyl ethers of ribose or deoxyribose by replacement of the acetal benzyl groups by bromide and coupling with the mercury salts of nucleic bases. The benzyl ether groups are removed by treatment with ammonia (Fischer-Helferich method not shown). In the case of pyrimidine nucleosides, one usually converts the lactams first to aromatic di-trimethylsilane ethers, which then react in high yields with protected halogenoses (Scheme 8.5.4)... 

Similarly, the effects of molecular weight, as well as other specific structural influences, were observed for other polarographic phenomena in which adsorbability plays an important role adsorption currents were observed especially for substances of higher molecular weight containing hydrophobic groups, e.g. for those with more condensed aromatic rings. In some instances free radicals are adsorbed and a chemisorption can be assumed. Such adsorption probably also operates in the adsorption of mercury compounds. Another factor which can play a role in the adsorbability of mercury salts is the polymerization of those salts. 

Another set of conditions (mercury salt-Br2, hv) for effecting the Hunsdiecker reaction has been recorded. This method, which is a combination of previously reported alternatives, gives yields of aryl bromides in the region of 80—90% except for electron-rich aromatics. 

Conversion of acetylenes into substituted maleate esters (62) by addition of two carboxy-groups to the unsaturated system is achieved using palladium and mercury salts in the presence of carbon monoxide. Diphenylacetylene and aromatic nitro-derivatives in the presence of carbon monoxide and... 

A convenient one-step conversion of aromatic nitro compds. to phenols with benzaldoxime has been reported High yields of alcohols, ethers, carboxylates, and nitrates can be obtained from alkyl halides with mercury salts... 

The mechanisms of the electrophilic substitutions in the isoxazole nucleus have not yet been studied. They should not differ fundamentally from those usually accepted for the substitution of aromatic systems but the structural specificity of the isoxazole ring might give rise to some peculiarities, as recently specially discussed.One important point is that isoxazole shows a clearcut tendency to form coordination compounds. Just as pyridine and other azoles, isoxazoles coordinate with halogens and the salts of heavy metals, for example of cadmium,mercury,zinc. Such coordination... 

Subshtuted 3-alken-l-ynes can be hydroaminated with primary or secondary aliphahc or aromatic amines at the alkynyl sites or at the alkynyl and at the alkenyl sites in the presence of Hg(ll) salts. However, the reachon is essentially stoichiometric in nature, even if the mercury compound can be recycled without apparent loss of achvity [262-264]. 

Picric acid, in common with several other polynitrophenols, is an explosive material in its own right and is usually stored as a water-wet paste. Several dust explosions of dry material have been reported [1]. It forms salts with many metals, some of which (lead, mercury, copper or zinc) are rather sensitive to heat, friction or impact. The salts with ammonia and amines, and the molecular complexes with aromatic hydrocarbons, etc. are, in general, not so sensitive [2], Contact of picric acid with concrete floors may form the friction-sensitive calcium salt [3], Contact of molten picric acid with metallic zinc or lead forms the metal picrates which can detonate the acid. Picrates of lead, iron, zinc, nickel, copper, etc. should be considered dangerously sensitive. Dry picric acid has little effect on these metals at ambient temperature. Picric acid of sufficient purity is of the same order of stability as TNT, and is not considered unduly hazardous in regard to sensitivity [4], Details of handling and disposal procedures have been collected and summarised [5],... 

Carbon dioxide Sulfur dioxide Aliphatic hydrocarbons Aromatic hydrocarbons Cholinesterase inhibitors Paraquat Lead Arsenic Mercury Removal from exposure and administer oxygen Removal from exposure Removal from exposure Removal from exposure Atropine, pralidoxime Gastric lavage and dialysis Dimercaprol, penicillamine Dimercaprol, penicillamine Dimercaprol (elemental), penicillamine, dimercaprol (inorganic salts)... 

The ratio of the two products is primarily affected by the nature of the mercury(II) salt and also by the reaction conditions. Since the formation of these compounds could result from either a kinetically or a thermodynamically controlled mercuration process, a study of the mercuration of 3 in the presence of aromatic amines using various mer-cury(II) salts has been more recently carried out in order to determine the conditions under which aminomercuration is reversible, and the results have been compared to those of the oxymercuration170. 

Other metals capable of electrophilic substitution of C-H bonds are salts of palladium and, environmentally unattractive, mercury. Methane conversion to methanol esters have been reported for both of them [29], Electrophilic attack at arenes followed by C-H activation is more facile, for all three metals. The method for making mercury-aryl involves reaction of mercury diacetate and arenes at high temperatures and long reaction times to give aryl-mercury(II) acetate as the product it was described as an electrophilic aromatic substitution rather than a C-H activation [30],... 

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