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Alkene Transfer Hydrogenation with Alkaline‐Earth Metal Catalysts
Author(s) -
Bauer Heiko,
Thum Katharina,
Alonso Mercedes,
Fischer Christian,
Harder Sjoerd
Publication year - 2019
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201813910
Subject(s) - alkene , catalysis , transfer hydrogenation , dehydrogenation , chemistry , hydride , styrene , isomerization , photochemistry , medicinal chemistry , deprotonation , polymerization , metal , polymer chemistry , organic chemistry , ruthenium , polymer , copolymer , ion
The alkene transfer hydrogenation (TH) of a variety of alkenes has been achieved with simple AeN′′ 2 catalysts [Ae=Ca, Sr, Ba; N′′=N(SiMe 3 ) 2 ] using 1,4‐cyclohexadiene (1,4‐CHD) as a H source. Reaction of 1,4‐CHD with AeN′′ 2 gave benzene, N′′H, and the metal hydride species N′′AeH (or aggregates thereof), which is a catalyst for alkene hydrogenation. BaN′′ 2 is by far the most active catalyst. Hydrogenation of activated C=C bonds (e.g. styrene) proceeded at room temperature without polymer formation. Unactivated (isolated) C=C bonds (e.g. 1‐hexene) needed a higher temperature (120 °C) but proceeded without double‐bond isomerization. The ligands fully control the course of the catalytic reaction, which can be: 1) alkene TH, 2) 1,4‐CHD dehydrogenation, or 3) alkene polymerization. DFT calculations support formation of a metal hydride species by deprotonation of 1,4‐CHD followed by H transfer. Convenient access to larger quantities of BaN′′ 2 , its high activity and selectivity, and the many advantages of TH make this a simple but attractive procedure for alkene hydrogenation.