Tellurides, diaryl synthesis

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. 

On the basis that bis-organyl tellurides undergo Te/Li exchange by treatment with an organolithium reagent, if a thermodynamically more stable organolithium moiety is released,bis-(phenylethynyl) telluride has been employed as starting material for the synthesis of diaryl tellurides. ... 

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. 

Halogen-lithium exchange. Special uses of this method include functionalization of bromoallylamine, preparation of a-silylaldehydes, synthesis of alkenyl tri-flones, trifluoromethyl ketones, alkylidenecyclopentanes" and diaryl tellurides. ... 

First, Suzuki and coworkers reported Cul-mediated synthesis of diaryl tellurides via C—Te cross-coupling of aryl iodides with benzene teUurolate ions [194]. Catalytic protocol has been subsequently developed using Cul/l,10-phenanthroline L80 for the coupling of aryl iodides with organotellurolates [195] (Scheme 20.58). Further improvement was achieved in the coupling of ditellurides with boronic acid derivatives using copper-based catalytic systems, Cul-bpy [166], CuCl-bpy [196], and CuSO -5H2O/l,10-phenanthroline [197]. 

Sequential synthesis of the and anions by electrochemical reduction of the elements Se or Te provides a route to both dialky 1-di- and monoselenides and tellurides [35]. Ultrasound has also been used to promote the electrochemical synthesis of unsymmetrical diaryl chalcogenides typified by 4-phenylseleno- and -tellurobenzonitrile [228]. However, the rate enhancements observed when electrochemical reactions are exposed to ultrasound would appear to stem from the increase in mass transport rather than cavitational effects [229]. 

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