The Open Organic Chemistry Journal

2012, 6 : 1-11
Published online 2012 January 19. DOI: 10.2174/1874095201206010001
Publisher ID: TOOCJ-6-1

Linear Triphosphines as Ligands for Metal Complexes Immobilization in Ionic Liquids: Palladium-Catalyzed Methoxylation of Alkynes

Lydie Harmand , Samer Saleh , Jacques Andrieu , Helene Cattey , Michel Picquet and Jean-Cyrille Hierso
Institut de Chimie Mole culaire de l'Universite de Bourgogne (ICMUB) - UMR 5260 CNRS 9, av. Alain Savary 21078 DIJON, France.

ABSTRACT

Several novel palladium triphosphine complexes have been synthesized and tested as recyclable catalysts for the methoxylation of alkynes into acetals in ionic liquids. A complete conversion of phenylacetylene was achieved with only 0.2% of [Pd(Triphos)NCMe][(PF6)2] in a methanol/[BMIM][BF4] mixture. We discovered that the addition of an ionic liquid to methanol allowed not only to increase the activity of the palladium catalyst but also to provide a recyclable catalyst which can be reused several times with a weaker drop of activity. To complete these catalytic studies, we describe the synthesis of the first poor σ-electron-donating/strong π-electron-acceptor linear Triphosphine which, after palladium coordination, led to a better selectivity compared to its Triphos analogue. The performances of recovered ionic liquid re-action mixtures show for the first time that P-tridentate ligands efficiently immobilize palladium catalysts and lead to se-lective catalytic systems benign for environment.