From 2- 2-R-ethen-l-yl -phenyl Methyl Tellurium Dibromides

From 2-(2-R-ethen-l-yl)-phenyl Methyl Tellurium Dibromides 

Refluxing 2-(2-R-ethen-l-yl)-phenyl methyl tellurium dibromides in pyridine for one hour produced 2-R-benzotellurophenes These reactions probably proceed via 2-(2-R-ethenyl)-phenyl tellurium bromide. 

On treatment with selenium dioxide in pyridine or potassium dichromate in acetic acid, 2/7-1-benzotellurins are converted to 2-formylbenzotellurophenes.  

The starting materials with a methyl group at the 2-, 4-, 7-, or 8-position produced 2-acetylbenzotellurophenes. The presence of a methyl group at the 3-position prevented the ring contraction.  

2-Formyl-3-methylbenzoteIlurophene 5.15 g (20 mmol) of 4-mcthyl-2//-1-benzotellurin are dissolved in 30 ml of pyridine, 1.1 g (10 mmol) of selenium dioxide are added, and the mixture is heated with stirring at 100° for 0.5 h. The resultant mixture is filtered, the filter cake is washed with 5 ml of pyridine, and the combined filtrate and washings are poured into hydrochloric acid containing pieces of ice. The hydrolyzed mixture is extracted with two 50 ml portions of chloroform, the combined chloroform extracts are washed with water, dried with anhydrous magnesium sulfate, filtered, and the solvent is distilled off. The residue is recrystallized from hexane/benzene yield 2.2 g (40%) m.p. 106-109°. 

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