Stereoselective Semihydrogenation of Alkynes by Nickel(0) Nanoparticles

Significance

The high-yielding and highly selective reduction of alkynes to alkenes has been a valuable transformation for a long time. The authors report a nice simple procedure for the preparation of Ni(0) nanoparticles that are extremely effective for the semihydrogenation of internal alkynes. Simple mixing of anhydrous NiCl₂ and lithium, DTBB and an alcohol in THF for only ten minutes provides the active nanoparticles. The scope of substrates is large including dialkyl-, hydroxyalkyl-, methoxyalkyl-, benzyloxyalkyl-, and amino­alkyl-substituted internal alkynes. All of them showed high conversion and selectivity. Terminal alkynes also afforded high yields with small amounts of over-reduction products.