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The Role of Binding Constants in the Efficiency of Chiral Catalysts Immobilized by Electrostatic Interactions: The Case of Azabis(oxazoline)–Copper Complexes

2004; Wiley; Volume: 10; Issue: 12 Linguagem: Inglês

10.1002/chem.200305739

1521-3765

José M. Fraile, José I. Garcı́a, Clara I. Herrerı́as, José A. Mayoral, Oliver Reiser, Antonio Socuéllamos, Heiko Werner,

Synthetic Organic Chemistry Methods

Abstract As shown by theoretical calculations, azabis(oxazoline)–copper complexes are considerably more stable than the analogous bis(oxazoline)–copper complexes. This enhanced stability allows them to be efficiently immobilized by means of electrostatic interactions to different anionic supports, such as clays and nafion–silica nanocomposites, without the loss of a ligand, as is observed for bis(oxazolines). As a result, enantioselectivities of around 90 % ee are obtained in the cyclopropanation reaction between styrene and ethyl diazoacetate. Moreover, the solid catalyst is easily recoverable.