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. 2013 Feb 25;32(4):1075-1084.
doi: 10.1021/om3012147. Epub 2013 Feb 11.

Biferrocene-Based Diphosphine Ligands: Synthesis and Application of Walphos Analogues in Asymmetric Hydrogenations

Afrooz Zirakzadeh  1 , Manuela A Groß, Yaping Wang, Kurt Mereiter, Felix Spindler, Walter Weissensteiner
Affiliations

Biferrocene-Based Diphosphine Ligands: Synthesis and Application of Walphos Analogues in Asymmetric Hydrogenations

Afrooz Zirakzadeh et al. Organometallics. .

Abstract

A total of four biferrocene-based Walphos-type ligands have been synthesized, structurally characterized, and tested in the rhodium-, ruthenium- and iridium-catalyzed hydrogenation of alkenes and ketones. Negishi coupling conditions allowed the biferrocene backbone of these diphosphine ligands to be built up diastereoselectively from the two nonidentical and nonracemic ferrocene fragments (R)-1-(N,N-dimethylamino)ethylferrocene and (SFc)-2-bromoiodoferrocene. The molecular structures of (SFc)-2-bromoiodoferrocene, the coupling product, two ligands, and the two complexes ([PdCl2(L)] and [RuCl(p-cymene)(L)]PF6) were determined by X-ray diffraction. The structural features of complexes and the catalysis results obtained with the newly synthesized biferrocene-based ligands were compared with those of the corresponding Walphos ligands.

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Figures

Chart 1
Chart 1
Scheme 1
Scheme 1
Scheme 2
Scheme 2
Figure 1
Figure 1
Molecular structures of (SFc)-2, (R,SFc,RFc)-3·BH3, (R,SFc,RFc)-16, (R,SFc,RFc)-17, [PdCl2(15)] (molecule 1), and [RuCl(p-cymene)(15)]PF6 showing 50% displacement ellipsoids. Hydrogen atoms and PF6– are omitted for clarity.
Scheme 3
Scheme 3
Scheme 4
Scheme 4
Chart 2
Chart 2
Figure 2
Figure 2
Superpositions of the molecular structures of [PdCl2(15)] and [PdCl2(SL-W002-1)] (left) and of [RuCl(p-cymene)(15)]PF6 with [RuCl(p-cymene)(SL-W002-1)]PF6 (right; only the cations of the ruthenium complexes are shown). Ligand 15 is shown in green and SL-W002-1 in blue. In both cases the Cp carbons C1–C5 and Fe1 are superimposed.
Chart 3
Chart 3. Substrates Used for Catalyst Screening
Chart 4
Chart 4
See this image and copyright information in PMC

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