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Séminaire Chimie ED459

Pd catalysts for the stereoselective synthesis of polycyclic aromatic compounds – from catalysis to all metal aromaticity

Prof. Max Malacria (ICSN Institut de Chimie des Substances Naturelles, UPR 2301 CNRS, Gif-sur-Yvette)

publié le , mis à jour le

Le Jeudi 22 janvier 2015 à 14h
ENSCM, amphithéâtre de Forcrand (attention, lieu et horaire modifiés)

Palladium/norbornene joint catalysis gives rise to a unique system in which the three most common formal oxidation states of the metal are at work in the same cycle (0, II, and IV) [1]. This presentation will summarize a selection of synthetic applications and the feasibility of Pd(IV) formation by oxidative addition of arylhalides. On this intermediate, the presence of a suitable chelating group could trigger unexpected aryl–norbornyl coupling, further broadening the scope of readily available polycyclic frameworks[2]. A straightforward total synthesis of a small panel of natural benzo[c]phenanthridines will be described [3].

In addition a straightforward access to dibenzo[c,e]azepines will demonstrate the performance of this joint palladium/norbornene organometallic catalysis. These synthetically challenging polycyclic frameworks are formed in a one pot procedure via a three-component coupling of an aryl iodide, a bromobenzylamine, and an olefin. A key, atroposelective aryl–aryl coupling from chelated Pd(IV) intermediates dictates the outcome of the cascade. DFT modeling sheds light on the complex mechanism that allows the complete diasteroselectivity to be observed [4].

Finally the first synthesis of C3-symmetric 44-core-valence-electron triangular palladium clusters, [{(SR’)(PR3)Pd}3]+ will be presented. Owing to delocalized metal–metal bonding, these stable complexes are the first noble-metal analogues of the aromatic cyclopropenyl cation [C3H3]+, with their all-metal aromaticity involving d-type atomic orbitals [5]. Moreover, the first application of metal-aromatic clusters in catalysis has been realized.

References

1. G. Maestri, N. Della Ca, E. Motti, E. Derat, M. Catellani, M. Malacria, J. Am. Chem. Soc. 2011, 133, 8574.
2. M.-H. Larraufie, G. Maestri, A. Beaume, E. Derat, C. Ollivier, L. Fensterbank, C. Courillon, E. Lacôte, M. Catellani, M. Malacria, Angew. Chem. Int. Ed. 2011, 50, 12253.
3. (a) G. Maestri, M-H Larraufie, E. Derat, C. Ollivier, L. Fensterbank, E. Lacôte, M. Malacria, Org. Lett. 2010, 12, 5692-5695. (b) P.-A. Deyris, T. Caneque-Cobo, F. Gomes, V. Narbonne, G. Maestri, M. Malacria, Heterocycles 2014, 807–815.
4. V. Narbonne, P. Retailleau, G. Maestri, M. Malacria, Org. Lett. 2014, 16, 628–631.
5. S. Blanchard, L. Fensterbank, E. Lacôte, G. Gontard, M. Malacria, G. Maestri, Angew. Chem. Int. Ed. 2014, 53, 1981–1991.

Contact local IBMM : Prof. Alberto Marra (équipe Glycochimie Reconnaissance Moléculaire)

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