Issue 24, 2007

Novel hydrido-ruthenium(ii) complexes with histidine derivatives and their application in the hydrogenation of ketones

Abstract

The complexes RuHCl((R)-binap)(L-NH2) with L-NH2 = (S)-histidine-Me-ester (1), histamine (3), (S)-histidinol (4) or 1-Me-(S)-histidine-Me-ester (5), and RuHCl((S)-binap)(L-NH2) with L-NH2 = (S)-histidine-Me-ester (2) have been prepared in 60–81% overall yields in a one-pot, three-step procedure from the precursor RuCl2(PPh3)3. Their octahedral structures with hydride trans to chloride were deduced from their NMR spectra and confirmed by the results of a single crystal X-ray diffraction study for complex 3. Under H2 and in the presence of KOtBu, complexes 1–5 in 2-propanol form moderately active catalyst precursors for the asymmetric hydrogenation of acetophenone to 1-phenylethanol. Complex 5 is more active and enantioselective than complexes 1–4, allowing complete conversion to 1-phenylethanol in 46% e.e. (R) in 72 h at 20 °C under 1 MPa of H2 with substrate : catalyst : base = 2000 : 1 : 30. Complex 5, when activated, also catalyzes the hydrogenation of trans-4-phenyl-3-buten-2-one to exclusively the allyl alcohol 4-phenyl-3-buten-2-ol under 2.7 MPa of H2 at 50 °C in 2-propanol. This selectivity for C[double bond, length as m-dash]O versus C[double bond, length as m-dash]C hydrogenation is consistent with a mechanism involving the outer sphere transfer of hydride and proton to the polar bond. Further extensions to complexes with peptides with N-terminal histidine groups appear feasible on the basis of the current work.

Graphical abstract: Novel hydrido-ruthenium(ii) complexes with histidine derivatives and their application in the hydrogenation of ketones

Supplementary files

Article information

Article type
Paper
Submitted
23 Feb 2007
Accepted
04 Apr 2007
First published
19 Apr 2007

Dalton Trans., 2007, 2536-2541

Novel hydrido-ruthenium(II) complexes with histidine derivatives and their application in the hydrogenation of ketones

C. Sui-Seng, A. Hadzovic, A. J. Lough and R. H. Morris, Dalton Trans., 2007, 2536 DOI: 10.1039/B702803B

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