Heterogeneous enantioselective catalysts: strategies for the immobilisation of homogeneous catalysts.
Enantioselective formation of C-H, C-C, C-O and C-N bonds has been extensively studied using homogeneous asymmetric catalysts for many years. However, these catalysts have yet to make a significant impact in the industrial synthesis of fine chemicals. A central reason is that homogeneous asymmetric catalyst design requires relatively bulky ligands and catalyst re-use through recovery and recycle often causes problems. One mechanism to overcome this problem is to immobilise the asymmetric catalyst onto a support and the resulting heterogeneous asymmetric catalyst can, in principle, be readily re-used. This tutorial review covers the different methodologies for immobilisation, including: adsorption, encapsulation, tethering using a covalent bond and electrostatic interaction and is aimed at both researchers new to the field and those with a wider interest in the immobilisation of homogeneous catalysts. Most importantly, recent studies will be highlighted that demonstrate that immobilised catalysts can give higher enantioselection when compared with their non-immobilised counterparts and the question of how high enantioselection can be achieved is addressed.
McMorn
Paul
P
Department of Chemistry, Cardiff University, P.O. Box 912, Cardiff, UKCF10 3TB.
Hutchings
Graham J
GJ
D000327:Adsorption; D002384:Catalysis; D002625:Chemistry, Organic / Q000379:methods*; D004800:Enzymes, Immobilized; D008956:Models, Chemical; D015394:Molecular Structure; D009930:Organic Chemicals / Q000737:chemistry; D009942:Organometallic Compounds / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D017641:Zeolites / Q000737:chemistry
D004800:Enzymes, Immobilized; D009930:Organic Chemicals; D009942:Organometallic Compounds; D017641:Zeolites; D012822:Silicon Dioxide