Preparation of copper(II)-BOX supported complexes and their application in stereoselective organic syntheses

Abstract

The synthesis of enantiomerically pure compounds is one of the major challenges in heterogeneous catalysis. The use of heterogeneous catalysts under ambient conditions offers several advantages compared with their homogeneous counterparts, such as ease of recovery and recycling. Bis(oxazoline) is one of the most popular classes of chiral legands, which has received a great deal of attention in coordination chemistry and in asymmetric catalysis. However, these ligands suffer from a drawback: a high catalyst-to substrate ratio is required to obtain good results. Their separation and recycling is therefore a prerequisite for their developmente as useful catalyst. This dissertation presents different methods of heterogenization of bis(oxazolines), these include immobilization by covalent (tethering or polymerization) or noncovalent bonding (ionic interchange); onto organic (polystyrene) or inorganic supports (silica, clays). It is presented the application of chiral Cu(II)-bis(oxazoline) complexes as heterogeneous catalysts for asymmetric cyclopropanation and Henry reaction, affording, in mild conditions, good level of stereo and enantioselection, as well as of recycling.