Tellurium insertion

In contrast, tellurium insertion in alkyl- or aryllithium compounds followed by alkylation is a useful method for the synthesis of unsymmetrical tellurides. (For a tabulation of unsymmetrical tellurides prepared by alkylation of organyl tellurolates, see ref. 8.)... 

The Grignard route to diorganyl ditellurides suffers from lack of generality and the mechanism of the oxidation seems to be uncertain. Alkylmagnesium halides demonstrate lack of reactivity towards elemental tellurium/ whereas aryhnagnesium halides in ether as the solvent furnish a mixture of ditellurides and tellurides. Satisfactory results are obtained by tellurium insertion in aryhnagnesium halides in THF followed by oxidation before or after aqueous work-up. ... 

Di-2-thienyl and di-2-furyl ditelluride are prepared from thiophene and furan by lithia-tion with n-buthyllithium, tellurium insertion and oxidative work-up. 

Treatment of 2,2 -dibromodiphenylacetylene 353 with /< /t-butyllithium followed by tellurium insertion resulted in ring closure to afford [l]benzotelluro[3,2-3][l]benzotellurophene 354 (Equation 6). Similarly, [l]benzoseleno[3,2-/ ]-[IJbenzoselenophene 355 and [l]benzothieno[3,2-3][l]benzothiophene 356 were also obtained <1998JHC725>. 

A double heterocyclic ring formation was also described. Treatment of 2,2 -dibro-modiphenylacetylene 35 with tert-butyllithium followed by tellurium insertion resulted in intramolecular ring closure to afford 111 ben/otel I uro 3,2-/ ] [l]benzotel I urophcnc 36 (Scheme 5). Similarly, 1I bcnzoseleno 3,2-/ I bcn/osclcnophcnc 37 and [l]benzothieno [3,2- ][l]benzothiophene 38 were also obtained [15]. 

Tellurium inserted into the Sn - Sn bonds of octakis[f-butyl]-l, 2,3,4-tetrastannetane to form 2,2,4,4-tetrakis[t-butyl]-l, 3,2,4-ditelluradistannetane2. 

Tellurium inserts into the P-group IV element bond in trialkylsilyl(-germyl, -stannyl)-diorganophosphanes in a benzene medium. The reaction proceeds via phosphane tellurides that rearrange to compounds with a P —Te-group IV element bond1-3. 

The reaction of tri-/-butyltriphosphirane with tellurium is the first example of a tellurium insertion into the P — P bond of a cyclophosphane. Tetra-/-butyltetraphosphetane does not react with tellurium1. 

Tellurium inserted into the Sb — Sb bond upon stirring a mixture of tellurium powder and tetraalkyldistibane in benzene at room temperature for several hours5. 

Tellurium inserts into the magnesium-carbon bond in aryl magnesium bromides. The resulting bromomagnesium arenetellurolates were not isolated but used in situ. Diethyl ether or tetrahydrofuran served as the reaction medium. 

Allyl Phenyl Tellurium4 (Tellurium Insertion) A 250-ml, three-necked flask is fitted with a reflux condenser, a magnetic stirrer, a gas inlet tube, and a dropping funnel. The flask is charged with 6.5 g (51 mmol) of tellurium powder and 80 ml of dry THF and the apparatus is flushed with argon or nitrogen. 26 ml (51 mmol) of a 2 M solution of phenyl lithium in diethyl ether are added dropwise to the stirred suspension and the... 

Bis[phenyltelluro]propane2 (Tellurium Insertion) A suspension of 12.8 g (0.1 mol) of tellurium powder in 100 ml tetrahydrofuran is frozen in a liquid nitrogen bath. 55.6 ml of a 1.8 molar solution of phenyl lithium (0.1 mol) in cyclohexane/dielhyl ether are injected. The mixture is allowed to thaw and is then stirred for 0.5 h at 20°. The mixture is then frozen again. 10.1 g (0.05 mol) of 1,3-dibromopropane are added, the mixture is allowed to thaw, magnetically stirred at 20° for 1 h, then hydrolyzed with 100 ml of an aqueous sodium chloride solution. The organic phase is separated, the aqueous phase extracted several times with... 

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