Parts-Per-Million of Soluble Pd Catalyze the Semi-Hydrogenation Reaction of Alkynes to Alkenes.

The synthesis of -alkenes is industrially carried out by selective semi-hydrogenation of alkynes with complex Pd catalysts, which include the Lindlar catalyst (PdPb on CaCO) and c-Pd/TiS (colloidal ligand-protected Pd nanoparticles), among others. Here, we show that Pd atoms are generated from primary Pd salts (PdCl, PdSO, Pd(OH), PdO) with H in alcohol solutions, independently of the alkyne, to catalyze the semi-hydrogenation reaction with extraordinarily high efficiency (up to 735 s), yield (up to 99%), and selectivity (up to 99%). The easy-to-prepare Pd species hold other potential catalytic applications.