Synlett 2002(6): 1011-1013
DOI: 10.1055/s-2002-31917
LETTER
© Georg Thieme Verlag Stuttgart · New York

Bidentate Camphane Phosphine Phosphinites as Ligands in Asymmetric Hydrogenation of α-Dehydroamino Acids

Axel Monsees*a, Sabine Laschat*b
Degussa AG Projekthaus Katalyse, Industriepark Höchst, G 830, 65926 Frankfurt am Main, Germany
Fax: +49(69)30527338; e-Mail: axel.monsees@degussa.com;
Institut für Organische Chemie, Technische Universität Braunschweig, Hagenring 30, 38106 Braunschweig, Germany
Fax: +49(531)3915388; e-Mail: s.laschat@tu-bs.de;
Further Information

Publication History

Received 27 March 2002
Publication Date:
07 February 2007 (online)

Abstract

The rhodium(I) catalyzed asymmetric hydrogenation of methyl (Z)-N-acetamido cinnamates 5a-c in the presence of camphor-derived phosphine phosphinites 4a-c gave the corresponding phenyl alanine derivatives 6a-c with good enantioselectivities (up to 89% ee) and high conversions.

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Selected spectroscopic data of phosphine phosphinite ligands:
4a: 1H NMR (500 MHz, CDCl3): δ = 0.72 (s, 3 H), 0.75-0.85 (m, 1 H), 0.94-1.05 (m, 1 H), 1.10 (s, 3 H), 1.34-1.45 (m, 1 H), 1.52-1.59 (m, 2 H), 1.79 (d, 1 H), 2.12 (d, broad, J = 13.8 Hz, 1 H), 2.12 (dd, J = 13.8/5.0 Hz, 1 H), 2.27 (d, J = 15.0 Hz, 1 H), 4.32 (t, J = 7.5 Hz, 1 H), 6.95-7.54 (m, 20 H); 31P NMR (202 MHz, CDCl3): δ = -24.0 (s), 112.2 (s).
4b: 1H NMR (500 MHz, CDCl3): δ = 0.71 (s, 3 H), 0.71-0.82 (m, 2 H), 0.92-1.00 (m, 1 H), 1.11 (s, 3 H), 1.36-1.42 (m, 1 H), 1.53-1.59 (m, 2 H), 1.83 (d, broad, J = 13.8 Hz, 1 H), 2.05 (s, 6 H), 2.11 (dd, J = 13.8/5.0 Hz, 1 H), 2.20 (s, 6 H), 2.26 (d, J = 15.0 Hz, 1 H), 4.25 (t, J = 7.5 Hz, 1 H), 6.72 (s, 1 H), 6.84 (s, 1 H), 6.94-7.51 (m, 14 H); 31P NMR (202 MHz, CDCl3): δ = -23.9 (s), 112.9 (s).
4c: 1H NMR (500 MHz, CDCl3): δ = 0.73 (s, 3 H), 0.73-0.85 (m, 2 H), 0.98 (s, 3 H), 0.90-1.85 (m, 28 H), 2.10 (dd, J = 13.8/5.0 Hz, 1 H), 2.33 (d, J = 13.8 Hz, 1 H), 3.90 (t, J = 7.5 Hz, 1 H), 7.05-7.55 (m, 10 H); 31P NMR (202 MHz, CDCl3): δ = -25.7 (s), 143.1 (s).