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Stereoselective Hydrodehalogenation via a Radical‐Based Mechanism Involving T‐Shaped Chiral Nickel(I) Pincer Complexes
Author(s) -
Rettenmeier Christoph,
Wadepohl Hubert,
Gade Lutz H.
Publication year - 2014
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.201403243
Subject(s) - geminal , chemistry , nickel , enantioselective synthesis , hydride , catalysis , enantiomer , radical , alkene , enantiomeric excess , medicinal chemistry , photochemistry , metal , stereochemistry , organic chemistry
We herein report the catalytic enantioselective hydrodehalogenation based on the interplay of a chiral molecular nickel(I)/nickel(II)hydride system. Prochiral geminal dihalogenides are dehalogenated via a secondary configurationally unstable, potentially metal‐stabilized radical intermediate. In a subsequent step, the liberated radical is then trapped by the nickel(II) hydrido complex, present in a large excess under the catalytic conditions, which in turn induces the enantioselectivity during the hydrogen atom transfer onto the radical intermediate. These new chiral nickel(I) complexes were found to catalyze the asymmetric hydrodehalogenation of geminal dihalogenides with moderate to good enantiomeric excess values using LiEt 3 BH as reductant. The main side product generally observed is the dehalogenated alkene, whereas the hydrodehalogenation of the chiral monohalogen compound occurred much more slowly despite the large excess of reductant.