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Unsymmetrical Iron P‐NH‐P′ Catalysts for the Asymmetric Pressure Hydrogenation of Aryl Ketones
Author(s) -
Smith Samantha A. M.,
Lagaditis Paraskevi O.,
Lüpke Anne,
Lough Alan J.,
Morris Robert H.
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.201701254
Subject(s) - aryl , catalysis , chemistry , medicinal chemistry , organic chemistry , alkyl
The reductive amination of α‐dialkylphosphine acetaldehydes with enantiopure β‐aminophosphines is a new, versatile route to unsymmetrical tridentate (pincer) ligands P‐NH‐P′. Four new ligands PR 2 CH 2 CH 2 NHCHR′CHR′′PPh 2 (R= i Pr, Cy, R′=Ph, CH(CH 3 ) 2 , R′′=Ph, H) prepared in this way are used to make the iron(II) complexes mer ‐FeCl 2 (CO)(P‐NH‐P′) and mer ‐FeCl(H)(CO)(P‐NH‐P′). The hydride complex with the rigid ligand with R′=R′′=Ph is an efficient and highly enantioselective homogeneous asymmetric pressure hydrogenation (APH) catalyst. Prochiral aryl ketones are reduced under mild conditions (THF, 0.1 mol % catalyst, 1 mol % KO t Bu, 5–10 bar, 50 °C) to the ( S )‐alcohols, usually in enantiomeric excess ( ee ) greater than 90 %. DFT calculations provided transition‐state structures for the enantiodetermining hydride‐transfer step.