COMMUNICATIONS
[3] For the activation of aryl mesylates and tosylates by Ni0 catalysts see:
a) V. Percec, J.-Y. Bae, D. H. Hill, J. Org. Chem. 1995, 60, 1060 1065;
b) Y. Kobayashi, R. Mizojiri, Tetrahedron Lett. 1996, 37, 8531 8534;
c) D. Zim, V. R. Lando, J. Dupont, A. L. Monteiro, Org. Lett. 2001, 3,
3049 3051.
[4] a) The importance of aryl alkyl cross-coupling is evident from the
following review: S. J. Danishefsky, S. R. Chemler, D. Trauner, Angew.
Chem. 2001, 113, 4676 4701; Angew. Chem. Int. Ed. 2001, 40, 4544
4568; for pertinent examples from our group see: b) A. F¸rstner, I.
Konetzki, J. Org. Chem. 1998, 63, 3072 3080; c) A. F¸rstner, I.
Konetzki, Tetrahedron 1996, 52, 15071 15078; d) A. F¸rstner, G.
Seidel, J. Org. Chem. 1997, 62, 2332 2336.
[5] a) M. Tamura, J. Kochi, J. Am. Chem. Soc. 1971, 93, 1487 1489;
b) S. M. Neumann, J. K. Kochi, J. Org. Chem. 1975, 40, 599 606;
c) R. S. Smith, J. K. Kochi, J. Org. Chem. 1976, 41, 502 509; d) J. K.
Kochi, Acc. Chem. Res. 1974, 7, 351 360.
[6] a) G. Cahiez, H. Avedissian, Synthesis 1998, 1199 1205; b) G. A.
Molander, B. J. Rahn, D. C. Shubert, S. E. Bonde, Tetrahedron Lett.
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108, 1812 1813; Angew. Chem. Int. Ed. Engl. 1996, 35, 1700 1701;
d) A. F¸rstner, H. Brunner, Tetrahedron Lett. 1996, 37, 7009 7012;
Mono- and Bidentate Phosphinanes–New
Chiral Ligands and Their Application in
Catalytic Asymmetric Hydrogenations**
Markus Ostermeier, Jan Prie˚, and G¸nter Helmchen*
Dedicated to Professor Dieter Hoppe
on the occasion of his 60th birthday
Chiral phosphanes possessing a modular make-up are
important as ligands for asymmetric catalysis with transition
metal complexes. The ethylene-bridged BPE ligands 2 and the
1,2-phenylene-bridged DuPHOS ligands,[1] introduced by
Burk et al., and analogues[2] belong to the most effective
ligands and were found to be particularly successful in
enantioselective hydrogenations. Even with the monodentate
phosphanes 1a and 1b enantiomeric excesses of up to 84 and
82% ee, respectively, were achieved in the hydrogenation of
¡
e) M. A. Fakhakh, X. Franck, R. Hocquemiller, B. Figadere, J.
Organomet. Chem. 2001, 624, 131 135.
R
R
[7] Vinylsulfones undergo similar reactions: J.-L. Fabre, M. Julia, J.-N.
Verpeaux, Tetrahedron Lett. 1982, 23, 2469 2472.
[8] T. Kauffmann, Angew. Chem. 1996, 108, 401 418; Angew. Chem. Int.
Ed. Engl. 1996, 35, 386 403, and literature cited therein.
( )n
( )m
P
R1
R1
( )n
( )n
P
P
R2
R
R
¬
[9] a) L. E. Aleandri, B. Bogdanovic in Active Metals: Preparation,
1a: n = 1; R1 = CH3, R2 = Ph 2a: m = n = 2; R = Me
1b: n = 2; R1 = Ph, R2 = Ph
2b: m = n = 2; R = Et
Characterization, Applications (Ed.: A. F¸rstner), VCH, Weinheim,
¬
1996, pp. 299 338; b) L. E. Aleandri, B. Bogdanovic, P. Bons, C. D¸rr,
A. Gaidies, T. Hartwig, S. C. Huckett, M. Lagarden, U. Wilczok, R. A.
Brand, Chem. Mater. 1995, 7, 1153 1170.
[10] EXAFS analyses indicate that [Fe(MgX)2] likely exists in form of
small clusters of this net stoichiometry, cf. refs. [9, 11].
acetamidocinnamic acid (3a) (Scheme 1); however, only
12% ee were obtained with 1a in the case of substrate
5b.[3, 4] With the chelate ligands 2a and 2b hydrogenations of
methyl 2-acetamidoacrylate furnished 91 and 98% ee, respec-
tively.[1b]
¬
[11] B. Bogdanovic, M. Schwickardi, Angew. Chem. 2000, 112, 4788 4790;
Angew. Chem. Int. Ed. 2000, 39, 4610 4612.
¬
[12] G. Siedlaczek, M. Schwickardi, U. Kolb, B. Bogdanovic, D. G.
Blackmond, Catal. Lett. 1998, 55, 67 72.
[13] Formally speaking, this corresponds to one of the elementary steps
that has to be passed through during the formation of [Fe(MgX)2]
from FeCl2 and RMgX.
[14] It is explicitly pointed out that all intermediates depicted in the
catalytic cycle are solely meant as a formal representation of the
reactive species but do not imply any structural information what-
soever.
[15] If the reduction of the aryl halides 1a c leading to the formation of 3
occurs via a radical pathway, the higher energy of the s* orbital of the
À
À
À
C Cl bond as compared to that of a C I or C Br bond might explain
the observed selectivities.
À
[16] The strongly covalent character of a Fe Mg bond is evident from
Scheme 1. Asymmetric catalytic hydrogenations. cod cycloocta-1,5-di-
ene, L* chiral ligand.
studies on well defined intermetallic complexes such as [Cp(dppe)-
À
Fe MgBr] (dppe 1,2-(diphenylphosphanyl)ethane): a) H. Felkin,
P. J. Knowles, B. Meunier, A. Mitschler, L. Ricard, R. Weiss, J. Chem.
Soc. Chem. Commun. 1974, 44; b) H. Felkin, P. J. Knowles, B.
Meunier, J. Organomet. Chem. 1978, 146, 151 167; c) G. B. McVicker,
Inorg. Chem. 1975, 14, 2087 2092.
Upon inspection of the literature it was observed that
4]
phosphetanes[5] (1, n 1) and phospholanes[1 (1, n 2) had
[17] a) M. S. Kharasch, E. K. Fields, J. Am. Chem. Soc. 1941, 63, 2316
2320; b) M. S. Kharasch, W. Nudenberg, S. Archer, J. Am. Chem. Soc.
1943, 65, 495 498.
[18] K. Kosswig in Ullmann×s Encyclopedia of Industrial Chemistry,
Vol. A25, VCH, Weinheim, 1994, pp. 747 817.
been studied intensively and phosphiranes[6] marginally,
surprisingly however, analogous phosphinanes (1, n 3) were
found to be unknown. Since there is a marked influence of
ring size on the properties of ligands, we decided to fill this
void in the arsenal of ligands. We now report the first ligands
[19] N. Alam, J. Hong, C. O. Lee, K. S. Im, B. W. Son, J. S. Choi, W. C. Choi,
J. H. Jung, J. Nat. Prod. 2001, 64, 956 957.
[20] A. F¸rstner, Angew. Chem. 2000, 112, 3140 3172; Angew. Chem. Int.
Ed. 2000, 39, 3012 3043.
[21] A. F¸rstner, C. Mathes, C. W. Lehmann, Chem. Eur. J. 2001, 7, 5299
5317, and references therein.
[22] a) A. V. Kavaliunas, A. Taylor, R. D. Rieke, Organometallics 1983, 2,
377 383; b) A. F¸rstner, Angew. Chem. 1993, 105, 171 197; Angew.
Chem. Int. Ed. Engl. 1993, 32, 164 189.
[*] Prof. Dr. G. Helmchen, Dipl.-Chem. M. Ostermeier, Dr. J. Prie˚
Organisch-chemisches Institut, Universit‰t Heidelberg
Im Neuenheimer Feld 270, 69120 Heidelberg (Germany)
Fax : (49)6221-54-4205
[**] This work was supported by the Fonds der Chemischen Industrie
¬
(Kekule scholarship for M. O.). We thank Dr. F. Rominger for the
X-ray crystal structure analysis.
612
¹ WILEY-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002
1433-7851/02/4104-0612 $ 17.50+.50/0
Angew. Chem. Int. Ed. 2002, 41, No. 4