Helically chiral polymers: A class of ligands for asymmetric catalysis
AUTOR(ES)
Reggelin, Michael
FONTE
National Academy of Sciences
RESUMO
Helically chiral polymers from achiral monomers containing N and P atoms have been shown to be ligands for transition metals such as Pd and Rh. The Rh complex of the phosphane-containing polyisocyanate p(18-co-17) was an active albeit hardly enantioselective catalyst in the asymmetric hydrogenation of the dehydro amino acid N-acetamidocinnamic acid (15% enantiomeric excess). The most active catalyst obtained until now was the Pd-complexed polymethacrylate Pd-p12, which catalyzes the allylic substitution reaction of 1,3-diphenylprop-2-enyl acetate with dimethyl malonate even at –20°C in quantitative yield, although again the enantioselectivity was unsatisfactory. The most successful application of a helically chiral polymer in asymmetric catalysis with respect to both reactivity and enantioselectivity is the polymethacrylate p(5-co-8). Its palladium complex catalyzes the above-mentioned reaction at 0°C with quantitative yield and 60% enantiomeric excess.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=397405Documentos Relacionados
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