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Semihydrogenation of Alkynes Catalyzed by a Pyridone Borane Complex: Frustrated Lewis Pair Reactivity and Boron–Ligand Cooperation in Concert
Author(s) -
Wech Felix,
Hasenbeck Max,
Gellrich Urs
Publication year - 2020
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202001276
Subject(s) - borane , frustrated lewis pair , hydroboration , intramolecular force , chemistry , alkyne , reactivity (psychology) , ligand (biochemistry) , boranes , catalysis , dissociation (chemistry) , boron , stereochemistry , coordination complex , photochemistry , lewis acids and bases , computational chemistry , medicinal chemistry , metal , organic chemistry , medicine , biochemistry , alternative medicine , receptor , pathology
The metal‐free cis selective hydrogenation of alkynes catalyzed by a boroxypyridine is reported. A variety of internal alkynes are hydrogenated at 80 °C under 5 bar H 2 with good yields and stereoselectivity. Furthermore, the catalyst described herein enables the first metal‐free semihydrogenation of terminal alkynes. Mechanistic investigations, substantiated by DFT computations, reveal that the mode of action by which the boroxypyridine activates H 2 is reminiscent of the reactivity of an intramolecular frustrated Lewis pair. However, it is the change in the coordination mode of the boroxypyridine upon H 2 activation that allows the dissociation of the formed pyridone borane complex and subsequent hydroboration of an alkyne. This change in the coordination mode upon bond activation is described by the term boron‐ligand cooperation.