om5b00790_si_004.xyz (328.01 kB)
Iridium-Catalyzed Asymmetric Hydrogenation with Simple Cyclohexane-Based P/S Ligands: In Situ HP-NMR and DFT Calculations for the Characterization of Reaction Intermediates
dataset
posted on 2015-11-09, 00:00 authored by Carlota Borràs, Maria Biosca, Oscar Pàmies, Montserrat DiéguezWe
report a reduced but structurally valuable phosphite/phosphinite-thioether
ligand library for the Ir-hydrogenation of 40 minimally functionalized
alkenes, including relevant examples with poorly coordinative groups.
We found that enantiomeric excesses are mainly dependent on the substrate
structure and on some ligand parameters (i.e., the type of thioether/phosphorus
moieties and the configuration of the phosphite group), whereas the
substituents of the biaryl phosphite moiety had little impact. By
tuning the ligand parameters we were able to find highly selective
catalysts for a range of substrates (ee’s up to 99%). These
phosphite/phosphinite-thioether ligands have a simple backbone and
thus yield simple NMR spectra that reduce signal overlap and facilitate
the identification of relevant intermediates. Therefore, by combining
HP-NMR spectroscopy and theoretical studies, we were also able to
identify the catalytically competent Ir-dihydride alkene species,
which made it possible to explain the enantioselectivity obtained.