Propargyl telluride

In disagreement with the above results, the propargyl-bromide of non-terminal acetylene gives only the corresponding propargyl telluride. ... 

The thio analogue behaves similarly, whereas the propargylic derivative is converted into the corresponding stable vinylic telluride. 

Alkynes conjugated to a triple bond are very reactive systems toward hydrotelluration. The reaction occurs in a shorter reaction time when compared to the reactions commented above. In this case, even disubstituted triple bonds give vinylic tellurides in good yields.41,42,139 140 In the case of non-symmetrical diynes, an order of reactivity is established for the hydrotelluration of triple bonds of the enyne systems (terminal > propargylic > alkyl substituted > aryl substituted).140 This order of reactivity is reflected in the preferential formation of the vinylic tellurides shown in Scheme 39. 

Propargyl bromide (2 mmol) was added at 0°C into a THE solution (5 mL) of n-BuTeLi (2 mmol), prepared from n-butyllithium (1.63 M, 1.23 mL, 2 mmol) and tellurium powder (256 mg, 2 mmol) at 0°C, and the reaction mixture was stirred for 15 min at the same temperature. At this stage, allenic telluride is formed and the resulting solution can be used for subsequent Li-Te exchange in the one-pot method. Allenic telluride was isolated quantitatively by removal of the solvent in vacuo, filtration using hexane (5 mL), followed by evaporation. The obtained telluride was essentially pure to show reasonable NMR spectra, but elemental analyses have not been successful because of the instability towards light and/or air. ... 

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