Heterogenized dialdimine ligands complexed to iridium were tested in the asymmetrictransferhydrogenation of acetophenone. E.e.s of up to 70% were achieved but the recycling was unsatisfactory. When such ligands were used in asymmetric epoxidation of styrene, a modest e.e. of 15% was achieved.
Design, Synthesis, and Characterization of Templated Metal Sites in Porous Organic Hosts: Application to Reversible Dioxygen Binding
作者:Anjal C. Sharma、A. S. Borovik
DOI:10.1021/ja0014739
日期:2000.9.1
Porous materials with immobilized metal complexes of defined structure have wide applications in catalysis, gas storage, and sensor technology. Reported herein is the use of template copolymerization methods to design and synthesize reversible dioxygen binding sites in a porous organic host. The immobilized metal sites are formed using molecular precursors including a substitutionally inert Co(III)
A templatepolymercomplex, which incorporates N-benzyl-D-valine with almost 100% stereospecificity, was synthesised by copolymerization of Δ-β2-[CO(R,R)-N,N′-bis[4-(p-vinylbenzyloxy)salicylidene]-1,2-diaminocyclohexane}(N-benzyl-D-valine)](3), styrene, and divinylbenzene, followed by dissociation of the co-ordinated aminoacid.
Templatesynthesis for Δ-β2-[Co(Schiffbase)(D-phe)] (Schiffbase = 4-(p-vinylbenzyloxy)-sal2-(R,R)-chxn) was carried out by copolymerizing the complex with styrene and divinylbenzene. After treating the formed polymercomplex gel with HCl, the gel took in D-phe preferentially (maximum optical purity = 74%), when it reacted with an excess of DL-PHE.
作者:Susanne Striegler、Michael Dittel、Rami Kanso、Natasha A. Alonso、Evert C. Duin
DOI:10.1021/ic200837z
日期:2011.9.19
A dormant macromolecular catalyst was prepared by polymerization of an aqueous styrene-butyl acrylate miniemulsion in the presence of a new polymerizable pentadentate ligand. The catalyst was activated by binding Cu(II) ions to the ligand site and then explored for its ability to hydrolyze glycosidic bonds in alkaline solution. The performance was correlated to the catalytic activity shown by low molecular weight analogs. A turnover rate of up to 43 x 10(-4) min(-1) was previously observed for cleavage of the glycosidic bond in selected p-nitrophenylglycosides with a binuclear, low molecular weight catalyst; by contrast, the same reaction is more than 1 order of magnitude faster and has a turnover rate of up to 380 x 10(-4) min(-1) when using the prepared macromolecular catalyst. The catalyzed hydrolysis is about 10(5)-fold accelerated over the uncatalyzed background reaction under the provided conditions, while a significant discrimination of the alpha- and beta-glycosidic bond or of the galacto- and gluco-configuration in the sugar moiety in the glycoside substrates is not observed.