3842
Organometallics 2005, 24, 3842-3848
About the Crystal Structure of [Rh((S,S)-DIPAMP)-
((Z)-2-benzoylamino-3-(3,4-dimethoxyphenyl)-methyl
Acrylate)]BF4: Major or Minor Catalyst-Substrate
Complex?†
Thomas Schmidt, Wolfgang Baumann,* Hans-Joachim Drexler,
Antonio Arrieta, and Detlef Heller*
Leibniz-Institut fu¨r Organische Katalyse an der Universita¨t Rostock e.V.,
Albert-Einstein-Strasse 29a, Rostock 18059, Germany
Helmut Buschmann
ESTEVE, Av. Mare de Deu de Montserrat 221, ES-08041 Barcelona, Spain
Received December 2, 2004
Asymmetric hydrogenation of (Z)-2-benzoylamino-3-(3,4-dimethoxyphenyl)-methyl acrylate
with [Rh((S,S)-DIPAMP)(MeOH)2]BF4 was investigated. Low temperature NMR measure-
ments prove the recently published X-ray structure of [Rh((S,S)-DIPAMP)((Z)-2-benzoyl-
amino-3-(3,4-dimethoxyphenyl)-methyl acrylate)]BF4 to be the major substrate complex. The
asymmetric hydrogenation of the prochiral DOPA precursor with the cationic Rh-DIPAMP
catalyst therefore follows the “anti-lock-and-key” motif analogue to similar substrate
complexes already known from literature.
Introduction
tioselectivity by its high reactivity, which was not
expected in those days, entered the literature as the so-
called major-minor concept or, according to Landis, anti
lock-and-key motif.
Since it has been experimentally proven in several
examples of asymmetric hydrogenation,1a,d,e it has to all
intents and purposes been developed to a basic concept
of homogeneous catalysis. The concept is, for example,
reflected in the ligand accelerated catalysis.3
The asymmetric hydrogenation supported by cationic
Rh(I) complexes is both one of the most intensively
investigated and best understood selection processes.
According to Halpern and Landis1 as well as Brown,2
the asymmetric hydrogenation proceeds as shown in the
general reaction sequence of Scheme 1.
In pre-equilibria diastereomeric substrate complexes
are formed by coordination of a prochiral olefin to the
catalyst-solvent complex as the active species. These
intermediates react in a sequence of elementary steps
(oxidative addition of hydrogen, insertion, and reductive
elimination) to the enantiomeric products.
Halpern and Brown were able to show for hydrogena-
tion of different R-dehydroamino acid derivatives that
the main source of selectivity seems to be the ratio of
the rate constants for oxidative addition of hydrogen
(k2min/k2maj). Relative stability of the intermediates
obviously does not play an important role.1f The result,
that the less stable intermediate dominates the enan-
Detailed investigations concerning mechanism4 or
rather activation of hydrogen as well as insertion under
use of isotope effects,5 detection of dihydrido-catalyst-
substrate complexes,6 reversibility of product forma-
tion,7 extended models,8 influence of electronic effects,9
and interconversion of the diastereomeric substrate
complexes10 have been published.
(3) Berrisford, D. J.; Bolm, C.; Sharpless, K. B. Angew. Chem., Int.
Ed. 1995, 34, 1059-1070.
(4) (a) Kimmich, B. F. M.; Somsook, E.; Landis, C. R. J. Am. Chem.
Soc. 1998, 120, 10115-10125. (b) Ayers, T. A.; RajanBabu, T. V. Process
Chem. Pharm. Ind. 1999, 327-345. (c) Landis, C. R.; Feldgus, S.
Angew. Chem., Int. Ed. 2000, 39, 2863-2866. (d) Feldgus, S.; Landis,
C. R. J. Am. Chem. Soc. 2000, 122, 12714-12727.
(5) (a) Landis, C. R.; Brauch, T. W. Inorg. Chim. Acta 1998, 270,
285-297. (b) Landis, C. R.; Hilfenhaus, P.; Feldgus, S. J. Am. Chem.
Soc. 1999, 121, 8741-8754.
† Dedicated to Gu¨nther Wilke on the occasion of his 80th birthday.
* To whom correspondence should be adressed. E-mail:
detlef.heller@ifok-rostock.de. Phone: +49 381 1281183; Fax: +49 381
(1) (a) Chan, A. S. C.; Pluth, J. J.; Halpern, J. J. Am. Chem. Soc.
1980, 102, 5952-5954. (b) Halpern, J. Science 1982, 217, 401-407.
(c) Halpern, J. Asymmetric Synthesis; Morrison, J. D., Ed.; Academic
Press: Orlando, 1985; Vol. 5, pp 41-69. (d) Landis, C. R.; Halpern, J.
J. Am. Chem. Soc. 1987, 109, 1746-1754. (e) McCulloch, B.; Halpern,
J.; Thomas, M. R.; Landis, C. R. Organometallics 1990, 9, 1392-1395.
(f) Giovannetti, J. S.; Kelly, C. M.; Landis, C. R. J. Am. Chem. Soc.
1993, 115, 4040-4057.
(6) Harthun, A.; Kadyrov, R.; Selke, R.; Bargon, J. Angew. Chem.,
Int. Ed. 1997, 36, 1103-1105.
(7) Harthun, A.; Selke, R.; Bargon, J. Angew. Chem., Int. Ed. 1996,
35, 2505-2507.
(8) Heller, D.; Thede, R.; Haberland, D. J. Mol. Catal. A: Chem.
1997, 115, 273-281.
(9) RajanBabu, T. V.; Radetich, B.; You, K. K.; Ayers, T. A.;
Casalnuovo, A. L.; Calabrese, J. C. J. Org. Chem. 1999, 64, 3429-
3447.
(2) (a) Brown, J. M.; Chaloner, P. A. J. Chem. Soc., Chem. Commun.
1980, 344-346. (b) Brown, J. M.; Chaloner, P. A. Homogeneous
Catalysis with Metal Phosphine Complexes; Pignolet, L. H., Ed.;
Plenum Press: New York, 1983; pp 137-165. (c) Brown, J. M. Chem.
Soc. Rev. 1993, 22, 25-41.
(10) (a) Brown, M.; Chaloner, P. A.; Morris, G. A. J. Chem. Soc.,
Chem. Commun. 1983, 664-666. (b) Brown, J. M.; Chaloner, P. A.;
Morris, G. A. J. Chem. Soc., Perkin Trans. 2 1987, 1583-1588. (c)
Bircher, H.; Bender, B. R.; von Philipsborn, W. Magn. Reson. Chem.
1993, 31, 293-298. (d) Casalnuovo, A. L.; RajanBabu, T. V.; Ayers, T.
10.1021/om0490536 CCC: $30.25 © 2005 American Chemical Society
Publication on Web 07/06/2005