Catalytic, -Selective, Semi-Hydrogenation of Alkynes with a Zinc-Anilide Complex.

J Am Chem Soc

Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, 82 Wood Lane, White City, London W12 0BZ, United Kingdom.

Published: April 2023

The reversible activation of dihydrogen with a molecular zinc anilide complex is reported. The mechanism of this reaction has been probed through stoichiometric experiments and density functional theory (DFT) calculations. The combined evidence suggests that H activation occurs by addition across the Zn-N bond a four-membered transition state in which the Zn and N atoms play a dual role of Lewis acid and Lewis base. The zinc hydride complex that results from H addition has been shown to be remarkably effective for the hydrozincation of C═C bonds at modest temperatures. The scope of hydrozincation includes alkynes, alkenes, and a 1,3-butadiyne. For alkynes, the hydrozincation step is stereospecific leading exclusively to the syn-isomer. Competition experiments show that the hydrozincation of alkynes is faster than the equivalent alkene substrates. These new discoveries have been used to develop a catalytic system for the semi-hydrogenation of alkynes. The catalytic scope includes both aryl- and alkyl-substituted internal alkynes and proceeds with high alkene: alkane, : ratios, and modest functional group tolerance. This work offers a first example of selective hydrogenation catalysis using zinc complexes.

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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC10080692PMC
http://dx.doi.org/10.1021/jacs.3c02301DOI Listing

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