Synthesis and applications of polymer-bound chiral epoxidation catalysts

• Main Author: Liu, C. H.
• Published: Swansea University 2001
• Subjects: 541.39
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637928

We have prepared polymer-supported unsymmetrical chiral (salen)Mn complexes (<B>11.2</B>) for asymmetric epoxidations; the link to the polymer was made between a single hydroxypropyl group attached to a Katsuki complex and polystyrenecarboxyl chloride. The polymer is as enantioselective in its catalysis of epoxidation of dihydronaphthalene as the Katsuki complexes, but more easily recovered for reuse. Excellent enantioselectivity (≥94% ee) was achieved and the polymeric catalyst was recycled up to 5 times with minimal loss in enantioselectively. The immobilized chiral (salen)Mn complex was formed by treatment of a polystyrenecarboxyl chloride with an unsymmetrical chiral (salen) complex (<B>8.2</B>), treatment with NaPF<SUB>6</SUB>. Unsymmetrical ligand <B>8.1</B> was synthesised from (<I>R</I>)-3-formyl-2-hydroxy-6-(3-hydroxypropyl)-2'-phenyl-1,1'-binaphtalene (<B>7.1</B>) and (<I>R</I>)-3-formyl-2-hydroxy-2'-phenyl-1,1'-binaphthalene (<B>7.2</B>) <I>via</I> a 1<I>S,</I>2<I>S</I>-diaminocyclohexane bridge. <B>Chapters 1 and 2</B> introduce asymmetric epoxidation and functionalized polymers, respectively. They provide reviews of recent work in the field, including work on polymer-supported chiral (salen)Mn complex catalysts. <B>Chapter 3</B> outlines the nature of the research project. <B>Chapters 4-6</B> describe the syntheses of racemic salicylaldehyde derivatives that would eventually be incorporated into an unsymmetrical Katsuki complex. <B>Chapter 7</B> describes the application of the successful routes to homochiral substrates. <B>Chapter 8</B> discusses the preparation of the unsymmetrical chiral salen ligand (<B>8.1</B>) and (salen)Mn complexes (<B>8.2</B>).