Addition of alkali tellurides to acetylenes

Elemental tellurium, treated with strong aqueous alkali, undergoes an oxido-reduction disproportionation giving the corresponding telluride ion which reacts with acetylenes to give divinylic tellurides in modest yields.  

Simple systems such as KOH/H2O/DMSO and KOH/H O/HMPA at 100-120°C under pressure have been used. 

The yields were markedly increased by the addition of a reducing agent such as SnCl2. The reaction of elemental Te, phenylacetylene, KOH in hydrazine hydrate/ water/toluene was performed under three-phase catalytical system (in the presence of AlKjN+MeCr) giving (Z,Z)-distyryl telluride in 50% yield.  

In the presence of alkyl halides under pressurized acetylene, alkylvinyl tellurides in medium to good yields are obtained along with variable amounts of divinyl and dialkyl tellurides.  

Reaction of acetylene with Te-KOH-HMPA triad. A mixture of Te (19.2 g), KOH (16.8 g), H2O (8 mL) and HMPA (165 mL) was heated (110-120°C) in a 1 L steel autoclave under initial acetylene pressure of 10 atm (21 L of C2H2 in total) for 6 h. The reaction mixture was 

---