Symmetrical diaryl tellurides

Since symmetrical dialkyl and diaryl tellurides are the most employed in organic synthesis, and often exhibit structural or biological interest, their preparation will be examined in detail, focusing on the methods and procedures that are considered as the most popular. 

The synthesis of aromatic tellurides has been performed via the reaction of iodoarenes (0-, m- and p-iodonitrobenzene, and di- and tri-methyliodonitrobenzenes) with phenyltelluride in HMPA at 80-90 C, preferably in the presence of Cul. Yields range between 53 and 95%.218 Symmetrical diaryl tellurides (69 R = 3-Me, 4-Me, 2,4-Me2,2,4,6-Me3,4-MeO) were prepared in good yields from reaction of nonac-tivated aryl iodides with Na2Te in DMF at 60 "C.219 The mechanisms of these reactions, which are limited to the iodoarenes, have not been discussed. 

The main routes to symmetrical diorganyl tellurides involve the direct reaction of nucleophilic telluride dianions (usually as Nii Tc) with alkylating or arylating reagents. Otherwise the electrophilic tellurium tetrahalides react with aryhnagnesium reagents, giving diaryl tellurides. 

In strict correlation with the early method for the preparation of symmetrical diaryl tellurides by treatment of tellurium(IV) halides with 4 mol equiv of aryl Grignard reagent (see Section 3.1.2.4), dialkynyl tellurides are prepared starting from bromomagnesium and lithium acetylenic derivatives. ... 

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