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A Tethered Ru–S Complex with an Axial Chiral Thiolate Ligand for Cooperative Si–H Bond Activation: Application to Enantioselective Imine Reduction
Author(s) -
Wübbolt Simon,
Maji Modhu Sudan,
Irran Elisabeth,
Oestreich Martin
Publication year - 2017
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.201700304
Subject(s) - ruthenium , chemistry , imine , diastereomer , enantioselective synthesis , racemization , medicinal chemistry , hydrosilylation , ligand (biochemistry) , catalysis , stereochemistry , organic chemistry , biochemistry , receptor
An axial chiral version of the 2,6‐dimesitylphenyl group attached to sulfur is reported. Its multistep preparation starts from ( S )‐binol, and the thiol group is established by a racemization‐free thermal Newman–Kwart rearrangement. The new chiral thiolate ligand decorated with one mesityl group is used in the synthesis of a tethered ruthenium chloride complex. Its spectroscopic characterization revealed solvent‐dependent epimerization at the ruthenium center. The major diastereomer is crystallographically characterized. Chloride abstraction with tetrakis[3,5‐bis(trifluoromethyl)phenyl]borate (NaBAr F 4 ) yields the corresponding coordinatively unsaturated ruthenium complex with the Ru−S bond exposed. Si−H bond activation at this Ru−S bond proceeds in syn fashion but with moderate facial selectivity (d.r.=70:30), generating diastereomeric chiral‐at‐ruthenium hydrosilane adducts. Their application to catalytic imine hydrosilylation led to promising enantioinduction (40 % ee ), thereby providing proof of concept for asymmetric catalysis involving cooperative Si−H bond activation.