Tellurium, methylation

Bis(butyl tellurium)methyl sulphide, prepared from bis(bromomethyl)sulphide and n-BuTeLi by treatment with 2 equiv of n-BuLi, gives rise to the corresponding bis(lithium methylsulphide), which can be isolated under vacuum as a colourless powder and stored at -20°C for 6 months. It decomposes under argon at 60°C and ignites explosively upon contact with traces of air. 

Tellurium Methyl-[pentafluor-ethyl]-E12h, 440 (CH3 - C2F5)... 

Tellurium Methyl-(tris-[trimethyl-silylj-methyl]- E12b, 417 (R—Tel + H3C —Li)... 

The checkers distilled the anisole from calcium sulfate before use. This reagent functions not only as a reactant, but also as solvent. In some similar preparations the intermediate trichloride is rather insoluble, as in the case of bis(3-methyl-4-methoxyphenyl)tellurium dichloride. The addition of co-solvents such as bis-(2-methoxyethyl) ether is beneficial. ... 

Intramolecular chalcogen interactions may also stabilize reactive functional groups enabling the isolation of otherwise unstable species or their use as transient intermediates, especially in the case of selenium and tellurium. For example, tellurium(II) compounds of the type ArTeCl are unstable with respect to disproportionation in the absence of such interactions. The diazene derivative 15.23 is stabilized by a Te N interaction. Presumably, intramolecular coordination hinders the disproportionation process. Other derivatives of the type RTeX that are stabilized by a Te N interaction include 8-(dimethylamino)-l-(naphthyl)tellurium bromide, 2-(bromotelluro)-A-(p-tolyl)benzylamine, and 2-[(dimethylammo)methyl]phenyltellunum iodide. Intramolecular donation from a nitrogen donor can also be used to stabilize the Se-I functionality in related compounds." ... 

A treatment of 2-butyltelluroaniline with an equimolar amount of bromoacetic acid results in spontaneous cyclization of the formed telluronium salt 31 to give 1-butylbenzotellurazinonium bromide 30. That the alkylation occurs at the tellurium and not at the nitrogen atom of 2-butyltelluroaniline has been proved by the isolation of the methyl ester of 31 in 60% yield when the amine was coupled with methyl bromoacetate under the same reaction conditions. Elimination of butyl bromide from 30 readily occurs on heating of its DMF solution leading to 2//-l,4-benzotellurazin-3(4//)-one 32 in 90% yield. 

A -methyl-5//,7//-dibenzo[d,.g][l,5]telluroazocine 65, its thiooxide 67a (X=S, R= Me) (95JA6388). The same type of reaction with benzylamine and sodium selenide gives A-benzyl-5//,7//-dibenzo[d,g][l,5]telluroazocine selenoxide 67b (X = Se, R = CH2Ph). Reaction of the tellurium dibromide 66 with sodium sulfide carried out in the absence of the primary amines affords the eight-member Te,S-containing heterocycle 5//,7//-dibenzo[d,g][l,5]telluroazocine (92CL151). 

Dimethyl-I,l -biphenyl has been prepared by a wide variety of procedures, but few of these are of any practical synthetic utility Classical radical biarjl syntheses such as the Gomberg reaction or the thermal decomposition of diaroyl peroxides give complex mixtures of products m which 4,4 dimethyl-l.l -biphenyl is a minor constituent A radical process maj also be involved in the formation of 4,4 dimethyl-1, l -biphenyl (13%) by treatment of 4-bromotoluene with hydrazine hydrate 5 4,4 -Dimethyl-l,l -biphenyl has been obtained in moderate to good yield (68-89%) by treatment of either dichlorobis(4-methyl phenyl)tellurium or l,l -tellurobis(4-methylbenzene) with degassed Raney nickel in 2 methoxyethyl ether 6... 

Jeng EGS, Sun IW (1997) Electrochemistry of tellurium (IV) in the basic aluminum chloiide-l-methyl-3-ethylimidazolium chloride room temperature molten salt. J Electrochem Soc 144 2369-2374... 

The mechanism of tellurium resistance has been investigated using genetic manipulation similar to that of Se (see above) and cellular oxidant capacity apparently plays an important role.144,206 A few tellurite determinants - both chromosomal and plasmid encoded - have been identified in bacte-ria.113,147 192 207 208 Recent studies have focused on the role of methyltransf-erases in Te resistance. Liu et a/.111 determined that the E. coli gene tehB uses S-adenosyl methionine and a methyltransferase in tellurite detoxification, but while no methylated tellurium compounds (see below) were observed, a loss of tellurite was observed in tellurite-amended cultures and Te complexation was inferred.191... 

The FCLD has been particularly useful as a highly sensitive means of measuring volatile sulfur, selenium, and tellurium compounds in studies of bacterial methylation [67, 111-114], Because of its high sensitivity to phosphinate esters [68], the FCLD could potentially serve as a monitor for nerve gases. 

Photolysis of acetone forms methyl radicals, isolated as dimethyl-mercury, and acetyl radicals isolated as diacetyl. Photolysis of benzo-phenone forms phenyl radicals which remove a tellurium mirror to give diphenyltellurium. 

Porter has recently shown that decomposing tetramethylam-monium amalgam is a source of trimethylamine and methyl free radicals.148 When a current of nitrogen is passed over the amalgam, tellurium mirrors downstream are removed.148... 

The environmental impact of tin is appreciable, as it is one of the three most enriched metals—only lead and tellurium precede—in the atmospheric particular matter, as compared with the abundance of the element in the earth crust (2.2 ppm). Tin releases to the environment can be methylated by aquatic organisms, yielding organometallic species of toxicity comparable to that of methylated mercury5. 

It is now well established that organometallic compounds are formed in the environment from mercury, arsenic, selenium, tellurium and tin and hence were also deduced on the basis of analytical evidence for lead, germanium, antimony and thallium. Biological methylation of tin has been demonstrated by the use of experimental organisms. Methylgermanium and methyllead were widely found in the environment but it is debatable whether germanium and lead are directly methylated by biological activity in natural environment. 

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