Phenyl telluride

In contrast to the cathodic reduction of organic tellurium compounds, few studies on their anodic oxidation have been performed. No paper has reported on the electrolytic reactions of fluorinated tellurides up to date, which is probably due to the difficulty of the preparation of the partially fluorinated tellurides as starting material. Quite recently, Fuchigami et al. have investigated the anodic behavior of 2,2,2-trifluoroethyl and difluoroethyl phenyl tellurides (8 and 9) [54]. The telluride 8 does not undergo an anodic a-substitution, which is totally different to the eases of the corresponding sulfide and selenide. Even in the presence of fluoride ions, the anodic methoxylation does not take place at all. Instead, a selective difluorination occurs at the tellurium atom effectively to provide the hypervalent tellurium derivative in good yield as shown in Scheme 6.12. 

The oxidative addition of iodine to diorganotellurides has also been examined by stopped-flow spectroscopy. The initial fast reaction of iodine with diphenyltellur-ide (23), di-4-methoxyphenyltelluride (24), A,V-dimethyl-2-(aminomethyl)phenyl-telluride (17), and 2,6-di-tert-butyltelluropyran-4-one (25) displays inverted Arrhenius behavior (negative values of E ), which is consistent with a preequilibrium involving higher-order iodine species as shown in equation (6). The I4 species is the actual oxidant for diorganotellurides as shown in equation (7). Thus, the initial reaction is formation of the r i-association complex of I4 with the... 

In a range of anions PhZ (Z = O, S, Se, Te), for example, the thiophenolate ion (PhS ) effectively traps aryl radicals (Ar ), whereas the anion of phenyl selenide (PhSe ) is 20 times less active, and the phenolate anion (PhO ) is absolutely inactive. The reaction of aryl radicals with phenyl-telluride ions (PhTe ) proceeds in an abnormal fashion—both asymmetrical and symmetrical tellurides are produced (Rossi and Pierini 1980). 

Alkyl phenyl tellurides (general procedure) Li metal (1.4 g, 0.2 mol) in small pieces is added under N2 to a solution of diphenyl ditelluride (4.1 g, 10 mmol) in dry THF (100 mL). The mixture is stirred at room temperature for 6 h, unreacted lithium is removed using a spatula and the aUcyl halide (20 mmol) neat or in THF is added dropwise to the stirred yellowish-brown solution. The solution is stirred at room temperature for 30 min, and under reflux for an additional 30 min. The solvent is evaporated, and HjO (10 mL) and ether (25 mL) are added to the residue, mixing thoroughly. The ethereal phase is separated and evaporated. The residue is fractionally distilled under vacuum (yields 62-79%). 

Method a. (ji-Styryl) phenyl telluride. To a solution of methyltriphenylphosphonium iodide (0.405 g, 1 mmol) in dry THF (4 mL) at room temperature was added dropwise n-BuLi (2 mmol). After stirring at room temperature for 20 min the solution was cooled to -78°C and a solution of PhTeBr (0.28 g, 1 mmol in 2 mL THF) was added, followed by benzaldehyde (0.16 g, 1.5 mmol). The temperature was raised to room temperature and stirred for 3 h. The solvent was removed under vacuum and the residue incorporated on Si02 and purified by flash column chromatography (Si02/hexane) giving an oil. Yield 0.185 g (60%). E/Z=2. 

Allylic phenyl tellurides are converted into the corresponding allylic amines by imination with [iV-(p-toluene-sulphonyl)imino] phenyliodinane. The reaction proceeds via [2,31-sigma-tropic rearrangement of a tellurimide intermediate. 

Iodination of alkyl phenyl telluride with Mel/Nal (typical procedure Mel (0.20 mL, 3.21 mmol) and Nal (75 mg, 0.50 mmol) are snccessively added to a solution of 1-phenyl-tellnrododecane (149 mg, 0.40 mmol) in DMF (2 mL) under Nj. The mixture is stirred for 10 min at room temperature and then for 2 h at 55°C. It is quenched with HjO and extracted with hexane. The extract is dried (MgS04) and filtered through a short column of SiOj to give 1-iodododecane as a colourless oil (103 mg (87%)). 

Oxidation of alkyl phenyl telluride with excess meto-chloroperbenzoic acid (MCPBA) (3-5 equiv) in methanol affords the replacement of the phenyltellurium moiety by a methoxy group, giving the corresponding methyl ethers - (method A). This reaction. 

In the above procedures, the telluroxide xyn-elimination (see Section 4.7.1) was observed as a competitive interference only in the case of cycloheptyl phenyl telluride, where cycloheptene is formed in a yield of 45%. 

Methoxy)cyclohexyl phenyl telluride and cycloheptyl phenyl telluride (easily accessible by methoxy telluration of the corresponding cycloalkenes, see Section 4.4.S.3) and... 

The difference in stability between the cychc six- and seven-membered methoxy tel-luroxides is noteworthy. Indeed, while the cyclohexane derivative is stable and isolable, giving ring contraction on treatment with 1 equiv of MCPBA, the cycloheptane derivative is unstable, suffering telluroxide elimination (like cycloheptene formation from cyclohep-tyl phenyl telluride), as will be shown in Section 4.7. 

Detellurative methoxylation of alkyl phenyl tellurides (typical procedure)2-Methoxy 3-phenyltelluro-l,2,3,4-tetrahydronaphthalene (1.85 g, 5 mmol) is treated with MCPBA (3.3 g, 15 mmol) in MeOH (30 mL) at 25°C with stirring. After 1 h the mixture is treated with aqueous Na2S203 followed by aqueous NaHCOj and extracted with ether (3x30 mL). The extract is dried (MgS04) and evaporated, to leave a residue which is purified by Si02 TLC (eluting with hexane/EtOAc, 4 1) to afford pure tranx-2,3-dimethoxy-l,2,3,4-tetrahy-dronaphthalene (0.37 g, 1.94 mmol) and the c/x-isomer (0.15 g, 1.76 mmol (54%)). 

In a typical experiment, n-dodecyl phenyl telluride (0.160 g, 0.42 mmol) in benzene (1 mL) is treated with PhjSnH (0.361 g, 1.03 mmol) during 5 h at room temperature, furnishing n-dodecane (0.080 g (87%)). 

General procedure for telluroxide elimination by oxidation of alkyl phenyl tellurides in the presence of base. To a two-necked, round-bottomed flask (25 mL) containing alkyl phenyl telluride (1 mmol), triethylamine (1-2 mmol) and diethyl ether (5 mL) was added solid MCPBA (purity 80%) (2 mmol as pure MCPBA) portionwise at 25°C. The mixture was stirred with a magnetic stirrer for 2 h at the same temperature before being poured into... 

Correlate method reaction of alkyl phenyl tellurides with chloramines-T... 

The reaction of alkyl phenyl tellurides with excess chloramine-T (A -chloro-A -sodium-p-tolysulphonamide) in refluxing THF leads to olefins, presumably through a tellurosul-phimino intermediate. Owing to the high yields obtained, this method seems to be highly competitive with the telluroxide elimination. 

Olefins by reaction of alkyl phenyl tellurides with chloramine-T (typical procedure). A solution of 1-dodecyl phenyl telluride (0.198 g, 0.52 mmol) and commercial chloramine-T trihydrate (0.300 g, 1.0 mmol) in THF (5 mL) is refluxed for 40 min under Nj. After evaporation of the solvent, the residue is treated with hexane (20 mL), and then fdtered. The filtrate is passed through a short Si02 column with hexane, giving, after evaporation, 1-dodecene as a colourless oil (0.068 g (78%)). 

Hydroxyvinyl phenyl tellurides submitted to the carbonylation reaction in non-polar solvents (CH2CI2 or CHCI3) lead to butenoMes in moderate yields. ... 

Tellur oxide elimination. sec-Alkyl phenyl tellurides on oxidation with CIQH4CO3H in ether afford alkenes as the major product. In some cases a stable Te(IV) compound is formed, which undergoes elimination on pyrolysis.5... 

Allylic phenyl tellurides, prepared in situ from the corresponding halides and diphenyl ditelluride, were converted by Phi = NTs, through a [2,3] sigmatropic rearrangement of ylidic intermediates, into A-tosylated allylic amines, e.g. [49] ... 

Trialkylboranes were converted into alkyl phenyl selenides and alkyl phenyl tellurides by reactions with PhSeSePh and PhTeTePh in the presence of stoichiometric amounts of air.550 Vinyl selenides and tellurides were synthesized by treating vinylboronic acids or esters with phenylselenyl chloride in ionic liquids (Equation (114))551 or by palladium-catalyzed coupling reaction of diorgano ditellurides (Equation (115)).552... 

A reaction sequence starting with bis[phenyltelluro]mcthane leads to the insertion of a methylene group into the carbon-halogen bond of an alkyl halide. The bis[phenyltelluro] methane is reacted with butyl lithium to yield lithiomethyl phenyl telluride, which combines with an alkyl halide. The resulting alkylmethyl phenyl tellurium is converted to the tellurium dihalide, which in turn decomposes to an alkylmethyl halide when kept under vacuum at 250 6 or heated in DMF in the presence of a sodium halide at 100°7. 

Telluroformates 144 were prepared by the treatment of alcohols 143 with a solution of phosgene in toluene, followed by sodium phenyltelluroate, and were isolated as yellow/orange viscous oil in 74% yield. It seems reasonable to say that the saturated selenium-containing rings 145 were formed through intramolecular nucleophilic substitution of the benzylse-leno moiety in telluroformates 144 with decarboxylative loss of phenyl telluride (Scheme 15) <1998JOC3032>. 

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