Bis(oxazoline)-metal complexes immobilised by electrostatic interactions as heterogeneous catalysts for enantioselective Diels–Alder reactions

✍ Scribed by J.M Fraile; J.I Garcı́a; M.A Harmer; C.I Herrerı́as; J.A Mayoral

• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 129 KB
• Volume: 165
• Category: Article
• ISSN: 1381-1169
• DOI: 10.1016/s1381-1169(00)00423-4

✦ Synopsis

The immobilisation by cationic exchange of complexes of a bis(oxazoline) with Cu(II), Mg(II) and Zn(II) has been studied with two types of anionic solid, a laponite clay and a nafion-silica nanocomposite. The results obtained show that the cationic exchange depends on both the geometry of the complex and the nature of the cation. Whereas the immobilisation of square-planar complexes takes place easily, the situation is not the same for tetrahedral complexes. The solids prepared have been used as catalysts in a benchmark Diels-Alder reaction. These solids are efficient catalysts but the enantioselectivities are low, a fact that is related to the presence of non-chiral catalytic sites and to the nature of both the solid counter-ion and the bis(oxazoline) structure.