Carbonyl or Nitrosyl Compounds

The methylene group in 3-oxo-2,3-dihydrobenzotellurophene condenses with dimethyl-formamide, aromatic aldehydes, bis[ethoxy](dimethylamino)methane, and 4-nitroso-A(,(V-dimethylaniline.  

2-Benzylidene-3-oxo-2,3-dihydrobenzoteUurophene 0.5 g (2 mmol) of 3-oxo-2,3-dihydrobenzotellurophcne and 0.21 g (2 mmol) of benzaldehyde are dissolved in ethanol, the solution is stirred with cooling in an icc/water bath, and a solution of 0.2 g (5 mmol) of sodium hydroxide in ethanol is added dropwise. The resultant mixture is stirred for 0.5 h, water is added, and the precipitate is filtered off, washed with water, dried, and recrystallized from hexane/benzene yield (not given) m.p. 140 . 

2- Benzylidene-3-oxo-2,3-dihydrobenzotellurophenes were also obtained when 2-acetyl-phenyl tellurium bromide and aromatic aldehydes were refluxed in acetic acid in the presence of piperidine. 3-Oxo-2,3-dihydrobenzotellurophene could be the intermediate that condenses with the aldehydes.  

3- Oxo-2,3-dihydrobenzotellurophene refluxed in DMF for 48 h in the presence of air or treated with potassium hexacyanoferrate(III) in refluxing aqueous ethanol yielded dark blue telluroindigo. 

Telluroindigo 2.46 g (10 mmol) of 3-oxo-2,3-dihydrobenzotellurophene is dissolved in 150 ml of ethanol, 8.7 g (30 mmol) of potassium hexacyanoferrate (III) and 2.0 g (50 mmol) of potassium hydroxide are dissolved in 90 ml of water, and the two solutions are mixed. The resultant mixture is heated under reflux for 30 min, then i50 ml of water are added, and the precipitate is filtered off and recrystallized from dimethylformamide yield 1.78 g (73%) m.p. 350°. 

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