From Non-Cyclic Tellurium Compounds

The starting materials for the preparation of 1,3-benzotellurazoles are aromatic tellurium compounds that contain an amino functionality in an or/Ao-position to the tellurium atom. The reduction of 2-benzeneazophenyl tellurium trichloride with sodium borohydride in ethanol generates 2-aminohenzenetellurol. This compound is acylated with carboxylic acid anhydrides and the acylaminobenzenetellurol cyclized by treatment with concentrated 

The starting materials for the preparation of naphtho[l,2-d]-l,3-tellura7oles are a-tetralones, tellurium dioxide, hydroxylamine, and hydrochloric acid.  

4-Dimethoxyphenyl tellurium trichloride or bis [3,4-dimethoxyphenyl] ditellurium were nitrated, the ortho-miro compound reduced to the 1,2,5-oxatellurazole with hypophospho-rous acid, and this heterocyclic compound converted to the 5,6-dimethoxy-l, 3-benzotellur-azole . 

2-Acetylaminophenyl tellurium trichlorides, obtained from acetanilides and tellurium tetrachloride, were reduced with sodium borohydride to 2-acetamino-l,3-benzenetellurols that cyclized on treatment with concentrated hydrochloric acid to 1,3-benzotellurazoles. 

The 2-acetylamino-l,3-benzenetellurols required as the precursors of 1,3-benzotellurazoles, can be prepared from tellurium tetrachloride and 2-aminophenyl mercury chlorides. This method allows the synthesis of 1,3-benzotellurazoles with substituents in the para-position to the nitrogen atom.  

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