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Séminaire Chimie ED459

Asymmetric conjugate addition of arylboronic acids and aryltrialkoxysilanes : new reactions in palladium catalysis

Dr. Francesca Gini (IBMM, Equipe Nucléosides-Effecteurs Phosphorylés)

Le Jeudi 21 Février 2008 à 13h45
salle de cours SC-16.01 (UM2)

The asymmetric transition-metal catalyzed conjugate addition of organometallic reagents to alpha,beta-unsaturated carbonyl compounds is of great importance for the enantioselective formation of carbon-carbon bonds.[1] The well established copper-catalyzed conjugated addition of dialkylzinc reagents [2] and Grignard reagents [3] allows the introduction of alkyl substituents in very high yields and enantioselectivities. A complementary protocol for the introduction of aryl moieties is the rhodium-catalyzed asymmetric conjugate addition of arylboronic acids [4] and arylsiloxanes.[5]

The use of palladium-based catalysts has been limited for the competitive formation of the corresponding Heck coupling product. Nevertheless, there are example of palladium-catalyzed conjugate addition of arylboronic acids 6 and aryltrialkoxysilanes.[7]

Our research was aimed to the development of the first example of asymmetric palladium-catalyzed conjugate addition of arylboronic acids [8] and aryltriethoxysilane (Scheme 1).[9] The conjugate addition of arylboronic acids proceeds smoothly affording excellent yields and enantioselectivities for a large variety of cyclic and acyclic alpha,beta-unsaturated carbonyl compounds. In the addition of aryltriethoxysilanes instead the formation of side products arising from a palladium-catalyzed transfer hydrogenation was observed. The careful optimization of the reaction conditions, aimed to the enhancement of the transmetalation step, however, led to almost complete suppression of the side reaction.

(cf figure dans le version PDF)

References :

1. P. Perlmutter Conjugate Addition Reactions in Organic Synthesis ; Tetrahedron Organic Chemistry Series 9 ; Pergamon : Oxford, 1992.
2. Feringa, B. L. ; Naasz, R. ; Imbos, R. ; Arnold, L. A. In Modern Organocopper Chemistry ; Krause, N., Ed. ; Wiley-VCH : Weinheim, Germany, 2002 ; pp 224–258.
3. López, F. ; Minnaard, A. J. ; Feringa, B. L. Acc. Chem. Res. 2007, 40, 179.
4. Hayashi, T. ; Yamasaki, K. Chem. Rev. 2003, 103, 2829.
5. Oi, S. ; Taira, A. ; Honma, Y. ; Inoue, Y. Org. Lett. 2003, 5, 97.
6. (a) Nishikata, T. ; Yamamoto, Y. ; Miyaura, N. Angew. Chem., Int. Ed. 2003, 42, 2768. (b) Nishikata, T. ; Yamamoto, Y. ; Gridnev, I. D. ; Miyaura, N. Organometallics 2005, 24, 5025.
7. (a) Denmark, S. E. ; Amishiro, N. J. Org. Chem. 2003, 68, 6997. (b) Nishikata, T. ; Yamamoto, Y. ; Miyaura, N. Chem. Lett. 2003, 32, 752.
8. Gini, F. ; Hessen, B. ; Minnaard, A. J. Org. Lett. 2005, 7, 5309.
9. Gini, F. ; Hessen, B. ; Feringa, B. L. ; Minnaard, A. J. Chem. Commun. 2006, 710.

résumé - 84.8 ko



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