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Transfer Semihydrogenation of Alkynes Catalyzed by a Zero-Valent Palladium N-Heterocyclic Carbene Complex


  • This research was funded by the National Research School Combination Catalysis (project no. 2004–2008-UVA-Elsevier-02/03). G.M. was the recipient of a Socrates/Erasmus fellowship from the University of Parma. We thank Dr. G. Rothenberg for helpful discussions and a critical reading of the manuscript.


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Beyond Lindlar and without hydrogen: Transfer hydrogenation of internal alkynes catalyzed by a palladium(0) catalyst containing an N-heterocyclic carbene ligand gives Z alkenes without over-reduction to alkanes (see scheme). Contrary to most transfer hydrogenations, ketones are not reduced. As such, this is the first catalyst that shows excellent stereo- and chemoselectivity for the semihydrogenation of alkynes without the need for hydrogen gas.