Diaryl Ditelluride reactions

The low reactivity of aryl halides towards nucleophilic reagents makes their reaction with sodium ditelluride unattractive for the preparation of diaryl ditellurides. Low yields are obtained, like the similar reaction with sodium telluride (see Section 3.1.2.1). 

Diaryl ditellurides (general procedure) The aryltellurium trichloride is poured into 15 mol equiv of Na2S-9H20 heated (and melted) at 95-100°C in a beaker, with strong manual stirring. An exothermic reaction occurs. After 10 min at the same temperature, excess HjO is added. By cooling the ditelluride solidifies, and is collected by decantation or filtration. The yields are near to quantitative. 

A more convenient method due to the mild experimental conditions and high yields involves the reaction of diaryl ditellurides with diazomethane. ... 

Reaction of diaryl ditellurides with diazomethane-formation of diaryl telluroketals (typical procedure). Di-p-methoxyphenyl ditelluride (2.34 g, 5 mmol) in ether (30 mL) is treated dropwise, at 0°C and while stirring, with an ethereal solution of diazomethane until disappearance of the red colour of the ditelluride. Evolution of N2 ensues. The product is obtained by evaporation of the solvent. RecrystaUization from hexane or EtOH gives colourless crystals (2.41 g (100%) m.p. 98-99°C). 

Arenetellurinic anhydrides are formed from the mixed anhydrides by hydrolysis, but a more convenient one-pot procedure for their preparation involves the reaction of phenyliodine(III) dicarboxylate with diaryl ditellurides in the two-phase system CH2CI2/H2O 10%. ... 

S.3 Reaction of diaryl ditelluride with arenediazonium salts/CuXj ... 

Addition of aryl tellurolates to acetylenic ketones (general procedure) NaBH4 (0.55 g, 15 mmol) is added in small portions, under N2, to a solution of the diaryl ditelluride (5 mmol) in EtOH (20 mL) at room temperature. A solution of the acetylenic ketone (10 mmol) in EtOH (10 mL) is then added to the reaction mixture, with stirring. The resulting precipitate of the 2-carbonylvinyl telluride is filtered off and recrystallized from EtOH. 

Diaryldifluorotellurium compounds, e.g. 19, are formed in high yield by reaction of sulfur tetrafluoride with either diaryl tellurides or diaryl ditellurides.221... 

It is also relevant to record that several iron-carbonyl complexes with bridging, and in one case terminal, aryltellurol ligands have been prepared by reaction of Fe(CO)5, Fe(CO)12 or [ji-CpFe(CO)2]2 with diaryl ditellurides and which, together with complexes containing other transition metal carbonyls, e.g, ruthenium, osmium and manganese, provide a substantial number of interesting compounds.2... 

Reactions of diaryl ditellurides with [bis(acyloxy)iodo]arenes, on the other hand, lead to oxidative cleavage of the Te-Te bond, and afford aryltellurinic mixed anhydrides 15 (Scheme 8) [26]. When such oxidations are conducted in a medium containing aqueous sodium hydroxide, aryltellurinic anhydrides 16 are obtained [16]. 

Dihydrotellurophene-1,1-difluoride119 was formed in the low-temperature reaction of 2,5-dihydrotellurophene with xenon difluoride. Aryltellurium(Vl) fluoride was synthesized from diaryl ditelluride or aryltellurium(lV) fluoride120 while perfluorinated dimethyl or diphenyl tellurides are transformed only to difluorides121,122 (Scheme 51). 

Dialkyl (e.g., 30) and diaryl ditellurides (e.g., 31) are transformed into the corresponding diorganotellurium trichlorides (e.g., 32 and 33) by reaction with elemental chlorine,74,75 with thionyl chloride,4,76 or with sulphuryl chloride (Scheme 8).65,77... 

If the diaryl ditelluride is previously converted in situ into the corresponding tellurenyl halide, both the electrophilic tellurium moieties are used. (The stable crystaUine 2-naph-thylteUurenyl iodide (see Section 3.7) reacts similarly.) The reaction is of general application, giving high yields of the expected tellurides with aromatic, aliphatic, cycloaliphatic, vinylid and acetylenic Grignard reagents, under mild conditions. 

A mixture of the appropriate diaryl ditelluride (1 mmol) and sodium borohydride (2.2 mmol) in DMF (10 luL) was stirred under an N2 atmosphere at 50-60°C until the solution was clear. The mixture was allowed to cool to room temperature, an appropriate alkynylphenyliodonium tosylate (2 mmol and DMF (10 mL)) was added and stirring was continued at 70-80°C under N2. The course of the reaction was followed by TLC. When the reaction was completed, the mixture was cooled, diluted with water (15 mL) and the product was extracted with petroleum ether (3x 10 mL). The combined extracts were washed with water, and dried with MgS04. After removal of the solvent, the residue was chromatographed on a column of silica gel using CH2CI2 as eluent to give the acetylenic teUuride. 

Typical procedure To a solution of diaryl ditelluride (0.50 mmol) in dry MeCN (2 mL) under Nj was added dropwise SO2CI2 (0.081 g, 0.60 mmol) and the mixture was stirred at room temperature for 1 h. a-Allenoic acid (0.50 mmol) in dry MeCN (2 mL) was then added to above ArTeCl solution with stirring. After the reaction was complete, the mixture was concentrated and the residue purified by flash chromatography or preparative TLC to afford j8-organoteUurobutenolides. 

Geranyl phenyl sulphides or sulphones, Me2C=CHCH2CMe=CHCHXY (33 X = H Y = SPh or SOjPh), cyclized to cyclocitral derivatives under acid conditions, whereas the corresponding dithioacetal (33 X = Y = SPh) gives the thiochroman (34). The novel heterocycles (35) have been prepared by standard methods from the corresponding tellurochromanones. The critical step in the synthesis of the latter consists of reduction of the appropriate diaryl ditelluride with borohydride and subsequent reaction with 3-chloropropionic acid under carefully controlled conditions. 

Unsymmetrical diaryl sulfides (60 R = 2-NO2, 4-NO2, 2,4-(N02)2 R = H, 4-NMe2) were obtained in 80-97% yields from the reaction under PTC conditions of nitro-activated aryl halides with arenethiolates generated in situ from the reduction of the corresponding diaryl disulfides with aminoiminomethanesul-finic acid (61).192 Arylthiolates carrying electron-withdrawing substituents were not sufficiently reactive. The reaction could also be applied to the synthesis of diaryl selenides, but not of ditellurides. 

The diaryl or aryl alkyl tellurides are dense yellow oils or crystalline solids, which are easier to handle than the dialkyl tellurides of similar molecular weight. Some of the diaryl derivatives are almost odorless solids. The same comments are valid for the diorganoditellurides 4, which are dark red oils (aliphatic derivatives) and dark red solids (aromatic derivatives). It is recommended that solutions of tellurides or ditellurides should not be kept in contact with air, since an amorphous white solid will form after some time. For some compounds, this reaction with oxygen is very fast. Aliphatic derivatives are more air sensitive than the aromatic ones. In view of this fact, it is recommended to bubble nitrogen into the solutions while a column or thin-layer chromatographic separation is performed. Evaporation of the solvent, however, minimizes the air oxidation. Pure liquids or solids can be handled in air with no need for special precautions, but prolonged exposure to air and to ambient light should be avoided. 

Reaction of aryl diazonium tetrafluoroborate 90 and diaryl dichalcogenides (disul-fane, diselenide, and ditelluride) 91 under ball milling at ambient temperature was applied in the synthesis of unsymmetrical aryl chalcogenides 92 by Ranu et al. 

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