Polystyrene or Magnetic Nanoparticles as Support in Enantioselective Organocatalysis? A Case Study in Friedel-Crafts
Sara Ranjbar1, Paola Riente1, Carles Rodríguez-Escrich1
1Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institute of Science of Technology , Avda. Països Catalans, 16, 43007 Tarragona, Spain.
Abstract:
Heterogenized versions of the second-generation MacMillan imidazolidin-4-one are described for the first time. This versatile organocatalyst has been supported on 1% DVB Merrifield resin and Fe3O4 magnetic nanoparticles through a copper-catalyzed alkyne-azide cycloaddition (CuAAC) reaction. The resulting catalytic materials have been successfully applied to the asymmetric Friedel-Crafts alkylation of indoles with α,β-unsaturated aldehydes. While both catalytic systems can be easily recovered and admit repeated recycling, the polystyrene-based catalyst shows higher stability and provides better stereoselectivities.
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