Two representative Walphos analogues with an achiral 2,2″-biferrocenediyl backbone were synthesized. These diphosphine ligands were tested in the rhodium-catalyzed asymmetric hydrogenation of several alkenes and in the ruthenium-catalyzed hydrogenation of two ketones. The results were compared with those previously obtained on using biferrocene ligands with a -symmetric 2,2″-biferrocenediyl backbone as well as with those obtained with Walphos ligands. The application of one newly synthesized ligand in the hydrogenation of 2-methylcinnamic acid gave ()-2-methyl-3-phenylpropanoic acid with full conversion and with 92% ee. The same ligand was used to transform 2,4-pentanedione quantitatively and diastereoselectively into (,)-2,4-pentanediol with 98% ee.
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| http://dx.doi.org/10.1021/om401074a | DOI Listing |
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Walphos versus Biferrocene-Based Walphos Analogues in the Asymmetric Hydrogenation of Alkenes and Ketones.
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April 2014
Institute of Organic Chemistry, University of Vienna, Währinger Straße 38, A-1090 Vienna, Austria.
Two representative Walphos analogues with an achiral 2,2″-biferrocenediyl backbone were synthesized. These diphosphine ligands were tested in the rhodium-catalyzed asymmetric hydrogenation of several alkenes and in the ruthenium-catalyzed hydrogenation of two ketones. The results were compared with those previously obtained on using biferrocene ligands with a -symmetric 2,2″-biferrocenediyl backbone as well as with those obtained with Walphos ligands.
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Institute of Organic Chemistry, University of Vienna, Währinger Straße 38, A-1090 Wien, Austria.
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Inorganic Chemistry Research Group, Chemical Physics, Center for Chemistry and Chemical Engineering, Lund University, Box 124, 221 00 Lund, Sweden.
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