From vinyltellurenyl iodides and Grignard reagents

Diorganyl tellurides add to alkynes via a radical mechanism in the presence of a catalytic amount of a radical initiator such as AIBN or 2,2 -azobis(4-methoxy-2,4-dimethyl-valeronitrile) (In), as well as under irradiation by visible light (tungsten lamp), affording vinylic tellurides in a variable ZIE ratio.  

The examination of the structure of the formed products revealed that the fission of the telluride bonds occurs exclusively at C(sp )-Te rather than C(sp )-Te bonds, at tertiary C-Te rather than primary C-Te bonds, and at PhCHj-Te rather than n-Bu-Te 

The following scheme shows that (2-propargyloxyphenyl)acyltellurides and (2-propar-gyloxyalkyl)aryltellurides undergo an intramolecular version of the above radical addition, promoted respectively by photolysis (tungsten lamp) and irradiation in the presence of (Bu3Sn)2 or BujSnH/AlBN giving chromanone and furan vinyltelluro derivatives (see also Section 5.7). 

Diphenyl ditelluride, on irradiation with visible UghL effects the v/c-phenyltelluration of acetylenes, giving the corresponding bis-phenyltelluroalkenes in good yields.  

With non-activated acetylenes (R- -R (a)) the best resnlts are provided by irradiation with visible light (400 nm) at 40-70°C, giving exclnsively the E isomers. On irradiation in the near-nltraviolet (300 nm), lower yields are obtained, probably becanse of the reverse reaction to the starting materials. 

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