New chiral β-aminoalcoholic ligand immobilized on Fe3O4@SiO2 nanoparticles and its application on the asymmetric addition of dialkylzinc reagents to aldehydes

In recent years it is growing the interest in magnetic nanoparticles as supports for chiral ligands, in order to develop a nanostructured catalytic system which combines advantages of homogeneous and heterogeneous catalysis, that is, simple recovery and high catalytic efficiency [1]. In a previous work our research group has developed the highly efficient ligand L1 in the addition of diethylzinc to aromatic aldehydes [2] (Scheme 1), but our ultimate aim was to achieve an analogous of L1 that could be immobilized on magnetic nanoparticles in order to develop a magnetic recoverable heterogeneous catalyst. In this work we present the nanostructured catalyst L2, obtainable through a Copper-Catalyzed Azide Alkyne Cycloaddition (CuAAC) on azido functionalized silica coated magnetite nanoparticles. First we also tested the catalytic activity of a homogeneous phase analogous of L2, ligand L3, to verify its homogeneous phase catalytic activity in the addition of diethylzinc to aldehydes. In this communication we describe the use of L2 and L3 in the addition of dialkylzinc reagents to aldehydes. Particularly we confirmed the preserved catalytic activity of L3 through the addition of diethylzinc to several aldehydes. Furthermore, we obtained promising results in the addition of diethylzinc to benzaldehyde with the employment of L2. Further efforts are currently ongoing, both in homogeneous and heterogeneous phase, with several aldehydes and other dialkylzinc reagents