t BuOLi-promoted terminal alkyne functionalizations by aliphatic thiols and alcohols.

Selective radical addition to terminal alkynes is always a difficult task to achieve because it gives a mixture of stereo- and regioisomers. Herein we describe the selective addition of aliphatic thiols or alcohols to N -phenylpropiolamides (terminal alkynes) using lithium tert -butoxide ( t BuOLi) in ethanol as a promoter. Mechanistically, it has been shown that the reaction proceeded through the generation of a thiyl radical intermediate, and the amide group in N -phenylpropiolamide could help in the activation of the alkyne, which led to thioacetalization via the formation of a ( Z )-selective anti-Markovnikov vinyl sulfide. The ( Z )-selectivity during the formation of vinyl sulfides was controlled by an intramolecular sulfur⋯oxygen interaction.