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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)

published on , updated on

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.

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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.


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