Zusammenfassung
New fluorous-tagged azabis(oxazoline) ligands were prepared using the copper-catalyzed azide-alkyne cycloaddition as ligation method. The resulting ligands were tested in copper-catalyzed asymmetric benzoylations (up to 99% ee), nitroaldol (up to 90% ee), and Michael reactions (up to 82% ee). The combination of unpolar fluorinated alkyl chains and polar triazole moieties imposes properties that ...
Zusammenfassung
New fluorous-tagged azabis(oxazoline) ligands were prepared using the copper-catalyzed azide-alkyne cycloaddition as ligation method. The resulting ligands were tested in copper-catalyzed asymmetric benzoylations (up to 99% ee), nitroaldol (up to 90% ee), and Michael reactions (up to 82% ee). The combination of unpolar fluorinated alkyl chains and polar triazole moieties imposes properties that are beneficial for the catalysts with respect to recyclability and selectivity. The scope and limitation of this strategy in comparison to analogous catalysts immobilized on methoxypolyethylene glycol (MeOPEG) or polystyrene is discussed. Moreover, this study shows that the choice of solvent for a given reaction is crucial to arrive at highly recyclable bis(oxazoline) catalysts.
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