4H-Tellurine

Di-tert-butyl-4H-tellurin A solution of 1.60 g (5.0 mmol) of 2,6-di-ferf-butyl-4-oxo /7-tellurin in 15 mL dry tetrahydrofuran is placed into a flame-dried, 50 mL, two-necked flask equipped with a rubber septum cap and a dry-argon inlet. The flask is cooled to 0°C 7.5 mL of a 1.5 M solution (10.5 mmol) of diisobutyl aluminium hydride in toluene are dropped to the cold solution with the help of a syringe. The reaction is quenched by addition of 10 mL of moist diethyl ether. The resulting solution is poured into 100 mL diethyl ether. The organic phase is washed with three 25 mL portions of 5% hydrochloric acid and then with two 50 mL portions of brine, dried with anhydrous sodium sulphate, filtered and the filtrate concentrated. Cold pentane (5 mL) is added to the residual oil and the mixture is cooled to -20°C. The pentane is decanted from the yellow aystals. The decantate is chromatographed on sihca gel with dichloromethane as the mobile phase to give a yellow oil. Yield 62%. 

By treatment with halogens, the 4-oxo-4H tellurins are converted into the corresponding dihalides. ... 

A similar reaction with vinylacetylene in the absence of tin(II) chloride in a medium consisting of aqueous potassium hydroxide and DMSO gave bis[l,3-butadienyl] tellurium in 3% yield as a mixture of isomers with the cis-cis isomer as the predominant species3. The reaction of dilithium telluride with l,5-diphenyl-l,4-pentadiyn-3-one led to the formation of 2,6-diphenyl-4-oxo-4H-tellurin as the major product and of bis[1,5-diphenyl-3-oxo-5-ethoxypenta-l,4-dien-]-yl tellurium as a by-product5. 

The yellow crystals were recrystallized from hexanes and indentilied as 4-[2,6-di-tert.-butyl-4H-tellurin-4-yl]-2,6-di-tert-butyl-4H-tellurinx. 

Diorgano-4-oxo-4H-tellurins were formed in 37-67% yield from dilithium or disodium telluride and bis[organoethynyl] ketones2-5. 

An additional product, 2,6-diphenyl-l-cyanomethylidene-4-dicyanomethylidene-4H-tellurin (11% yield m.p. 259-262°) was isolated from the reaction of the 2,6-diphenyl-4-oxo-4/f-tellurin and malonitrile2. 4-Oxo-4//-tellurins also condensed with 4-alkylchalcogenium salts to yield 4-alkylidene-4//-tellurins3 4. 

When 2,6-diphenyl-4-methyl-l-tellurinium tetrafluoroborate and dimethylthioformamide were heated in acetic anhydride, 2,6-diphenyl-4-[2-(N,N-dimethyliminio)-ethylidene]-4H-tellurin tetrafluoroborate was isolated3. 

Diphenyl-4-formylmethylidene-4H-tellurin was obtained by hydrolysis of the dimeth-yliminio derivative with aqueous sodium hydrogen carbonate3. 

Methine dyes that contain a tellurine group are transformed by elemental halogens to 4H-tellurin 7e,7e-dihalides2, and by air or hydrogen peroxides to Te,re-dihydroxides 5. 

H-Tellurin 2,6-Dimethyl-4-oxo-E12b, 802 (1,4-Diin + Li2Te) Telluroxid Methyl-phenyl- (Hydrate) E12b, 645 (RR TeCI2 + NH3/ H20)... 

Methyltellurinium tetrafluoroborates condensed with 4-oxo-4//-tellurins to yield 4- (tellurinium-4-yl-methylidene ) -4H-tellurins ... 

Six-membered tellurium heteroarenes. 4H-Tellurines, 2H-tellurines, tellurinium salts, annelated tellurines, and heterocycles with tellurium and an additional heteroatom are known. 

---