Stereoselective Alkyne Hydrogenation by using a Simple Iron Catalyst

The stereoselective hydrogenation of alkynes constitutes one of the key approaches for the construction of stereodefined alkenes. The majority of conventional methods utilize noble and toxic metal catalysts. This study concerns a simple catalyst comprised of the commercial chemicals iron(II) acetylacetonate and diisobutylaluminum hydride, which enables the Z‐selective semihydrogenation of alkynes under near ambient conditions (1–3 bar H2, 30 °C, 5 mol % [Fe]). Neither an elaborate catalyst preparation nor addition of ligands is required. Mechanistic studies (kinetic poisoning, X‐ray absorption spectroscopy, TEM) strongly indicate the operation of small iron clusters and particle catalysts. Simple but effective: A catalyst comprised of commercial iron(II) acetylacetonate and diisobutylaluminum hydride enables the Z‐selective semihydrogenation of alkynes in high yields and with high stereocontrol. Neither elaborate catalyst preparation nor addition of ligands is required. Mechanistic studies indicate the operation of small Fe cluster catalysts.