Elimination of Tellurium

Heating diaryl tellurium dicarboxylates in acetonitrile with iodine or bromine in the presence of potassium fluoride produced aryl halides in low yields.  

Bis[4-methoxyphenyl] tellurium dicarboxylates heated with copper(I) cyanide in DMF at 160° produced 4-methoxyphenyl cyanide in very low yields.  

Diphenyl tellurium diacetate refluxed in acetic acid with styrene in the presence of palladium(II) chloride and sodium acetate, arylated styrene to stilbene and formed biphenyl.  

When bis[4-methoxyphenyl] tellurium diacetate in benzene solution was irradiated with light from a high-pressure mercury lamp, 4-acetyloxy-(methoxy)-benzene was formed in 6% yield.  

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Tetraphenyltellurophene fails to undergo Diels-Alder addition with maleic anhydride even when heated at 220 °C for 21 h. Tetraphenyltellurophene 1,1-dibromide, however, on heating with maleic anhydride undergoes elimination of tellurium to produce tetraphenyl-furan and/or the dibenzopentalene derivatives (76) and (77) (61JA4406). 

On treatment with concentrated hydrochloric acid and aluminum amalgam, l-telluracyclohexane-3,5-diones decompose with elimination of tellurium. Their chemical behavior is determined by the presence of the dicoordinate tellurium center and two carbonyl groups in their molecules. As cyclic diketones, compounds 12 readily form oximes and dioximes under treatment with hydroxylamine. The former reaction is preferably carried out in dilute acetic acid solution, whereas the latter is carried out in basic... 

Hydrogen bromide cleaves digermyl tellurium compounds to germyl bromides with elimination of tellurium as hydrogen telluride2. 

The solid compounds are colorless, whereas the oils, that cannot be distilled, are light yellow. The compounds are readily hydrolyzed by atmospheric moisture. They decompose with elimination of tellurium on heating or prolonged storage at 20°. 

The telluronoamides and telluronohydrazides are stable at 20° in the absence of moisture. Wet solvents or moisture cause elimination of tellurium. The compounds cannot be chromatographed on alumina or silica gel1. The telluronodimethylformamide obtained from cholesteryloxymethylene iminium chloride and sodium hydrogen telluride is a yellow, unstable solid2. 

These heterocyclic tellurium compounds react with phosphite and with C,C-multiple bonds, even below 20°, with elimination of tellurium. These compounds may, therefore, be useful as precursors of 1,3-heterodienes1. 

Irradiation of benzene solutions of 7e-aryl arenetellurocarboxylates with light from a mercury lamp generated radicals via homolytic cleavage of the Te—CO bond. The free radicals subsequently formed aldehydes, diorgano tellurium compounds, and diorgano ditellurium compounds via hydrogen abstraction, dimerization and elimination of tellurium, or dimerization -. The products of the photo-induced reaction of Te-4-methylphenyl 2-methylthiobenzene(tellurocarboxylate) are given as an example . ... 

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. 

The compound 92 is extremely light-sensitive. Under the action of phosphites or compounds with multiple bonds, it readily eliminates a tellurium atom and thus may be considered as a synthetic equivalent of the heterodiene 93a. 

Fig. 2 Reductive elimination of halogens from chalcogenopyrylium dyes 6-11 containing tellurium(IV) dihalide groups. 

The transfer of iodine to the organic substrate represents a formal reductive elimination at tellurium(lV) to give tellurium(ll) as well as oxidation of the alkene. In a series of diaryltellurium(lV) diiodides, iodination of organic substrates is accelerated by electron-withdrawing substituents and is slowed by electron-donating substituents, which is consistent with the substituent effects one would expect for... 

Once the thiol is introduced to the coordination sphere of the selenoxide or telluroxide, a second slower reaction occurs. This step is associated with reduction of the chalcogen(IV) oxidation state to the chalcogen(II) oxidation state, which was demonstrated with dihydroxy telluranes 52 and 53. In the tellurium(IV) oxidation state of 52 and 53, the 5p orbital of tellurium is involved in the three-center, four-electron bond and cannot interact with the carbon 7r-framework. Long-wavelength absorption maxima for 52 and 53 are found at 510 and 500 nm, respectively in water. Reductive elimination generates a tellurium(II) atom, whose 5p orbital can now... 

Diaryl ditellurides are relatively thermolabile compounds and eliminate one tellurium atom by heating at 300°C. ° In the presence of copper metal, however, the extrusion of tellurium is achieved during reflux with toluene or dioxane. " " ... 

The reaction involves an attack by the tellurium anion at the halogen atom followed by a rapid elimination of ketene from the resulting enolate. 

The reaction has been rationalized as involving an attack of lithium teUurolate on a lithi-ated sulphone, promoting the elimination of lithium phenyl sulphinate and the formation of a labile epitelluride that readily collapses into stilbene and elemental tellurium. 

Elimination of sulfur, selenium, tellurium compounds Selenoxides... 

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