Mercury aryl halides

The monoaryl boric acids, RB(OH)2, arc usually isolated, as stated al >o x, l)y the action of water on the type RBXg, aitliough in certain cases this leads to the formation of the oxide RBO. The phenyl eom >ound has l)ecn obtained b " boiling with water the product of reaction from magnesium phenyl bromide and boron trifluoride. The most remarkable feature of the type RE(OH)2 is that the action of iiiercuric chloride upon them leads to the production of mercury aryl halides (RHgX). The anisyl and phenetyl compounds do not yield oxides when heated, or form salts, and tlie jS-naphthyl acid exists in two modifications. Dehydration of the acids in maw gives the oxides, RBO. 

Some aryl iodides are known to generate the diaryImercury at a mercury cathode. In the case of 4-iodoaniso e, reduction at more negative potentials in dimeth-ylfonnamide leads to the formation of less di(4-methoxyphenyl)mercury. At glassy carbon, anisole is the only reduction product. 4-Bromoanisole gives only anisole at either mercury or carbon [143]. Mercur> has been used as cathode material for many preparative experiments with aryl halides but glassy carbon and also stainless steel are very satisfactory alternatives. 

Several organolithium compounds have important apphcations in organic syntheses. These may be readily synthesized by reactions of lithium with organics. The metal reacts with alkyl or aryl halides or mercury alkyls or aryls to produce alkyl or aryl hthium. Some examples are ... 

Some examples of electrosyntheses based on the reduction of monohalobenzenes are now cited. Reduction of iodobenzene and bromobenzene at mercury in carbon dioxide-saturated DMF containing TEAP affords benzoic acid in up to 40% yield [178]. Bromobenzene, 3-methoxybromobenzene, 4-bromofluorobenzene, 4-(trifluoromethyl)-chlorobenzene, and 1,2,4-trichlorobenzene can be converted into aldehydes at a cadmium-coated stainless-steel cathode in DMF containing TBABr [179]. In the presence of trimethylchlorosilane, silylation products arise from the reduction of various aryl halides at platinum in DMF containing TEAOTs [100]. Reduction of p-iodoanisole at... 

Although In(I) halides do not insert directly into aryl-halide bonds, oxidative arylation does occur with In(I) halides and aryimercuriais in good yields The aryl-mercurial may be an arylmercurial halide or the bis(aryl)mercurial ... 

Aryl halides containing less reactive halogen can also be converted into sulfides by thiols if heavy-metal (lead, zinc, mercury) thiols are used at 225-230° 1-naphthyl, 2-naphthyl sulfide,301 1- and 2-naphthyl phenyl sulfide,302 and 1-and 2-naphthyl o-, m-, and p-tolyl sulfide303 have been obtained in this way. When the heavy-metal thiolates are too stable and do not react with aryl bromides even at 240°, the aryl sulfides can nevertheless often be prepared by a generally applicable reaction of aryl iodides with sodium thiolates under the influence of copper as catalyst.304... 

A generally applicable method of preparing dialkyl- and diaryl-mercury compounds is by treatment of alkyl or aryl halides or alkyl sulfates with sodium amalgam 160... 

L. Yagupolskii [38] developed a method for trifluoromethylsulfanylation of aromatic and heterocychc compounds using trifluoromethylthiocopper. Remy [39] suggested carrying out the synthesis of aryltrifluoromethyl sulfides by generation CuSCFs (from trifluoromethylthio mercury and -copper) in situ with the aryl halides. This not only reduces the number of steps but also increases the overall efficiency (Scheme 9). 

F.t.i.r. spectra of both anomers of a variety of peracetylated 2,4-dinitrophenyl D-gluco- and galacto-pyranosides and peracetylated aryl 1-thioglycosides have been recorded. The anomers give characteristic absorptions. F.t.i.r. spectra of adducts formed between D-glucose and zinc(II), cadmium(II) and mercury(II) halides in the solid (KBr pellets) and in solution (film cast) have been discussed in detail. ... 

Aryl bromides were also perfluoroethylated under these conditions [205] The key to improved yields was the azeotropic removal of water from the sodium perfluoroalkylcarboxylate [205] Partial success was achieved with sodium hepta-fluorobutyrate [204] Related work with halonaphthalene and anthracenes has been reported [206 207] The main limitation of this sodium perfluoroalkylcarboxylate methodology is the need for 2 to 4 equivalents of the salt to achieve reasonable yields A trifluoromethylcopper solution can be prepared by the reaction of bis(tri-fluoromethyl)mercury with copper powder in /V-methylpyrrolidone (NMP) at 140 °C [208] (equation 138) or by the reaction of N-trifluoromethyl-A-nitro-sotnfluoromethane sulfonamide with activated copper in dipolar aprotic solvents [209] This trifluoromethylcopper solution can be used to trifluoromethylate aro matic [209], benzylic [209], and heterocyclic halides [209]... 

The reaction of heterocyclic lithium derivatives with organic halides to form a C-C bond has been discussed in Section 3.3.3.8.2. This cannot, however, be extended to aryl, alkenyl or heteroaryl halides in which the halogen is attached to an sp2 carbon. Such cross-coupling can be successfully achieved by nickel or palladium-catalyzed reaction of the unsaturated organohalide with a suitable heterocyclic metal derivative. The metal is usually zinc, magnesium, boron or tin occasionally lithium, mercury, copper, and silicon derivatives of thiophene have also found application in such reactions. In addition to this type, the Pd-catalyzed reaction of halogenated heterocycles with suitable alkenes and alkynes, usually referred to as the Heck reaction, is also discussed in this section. 

---