(+)-Cinchonine-Decorated Dendrimers as Recoverable Organocatalysts

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. First- and fourth-generation phosphorus dendrimers decorated on their surface with (+)-cinchonine moieties for the use as organocatalysts have been prepared. The first-generation dendrite showed the highest activity and enantioselectivity in the α-amination of several β-dicarbonyl compounds. A positive dendritic effect was observed. Its recovery and reuse over 10 cycles was demonstrated without loss of activity. Preliminary studies of the scope of the reaction have been performed. Large and practical: Three new supported organocatalysts containing two, twelve, and ninety six (+)-cinchonine moieties are prepared, and are found to catalyze the α-hydrazination of 1,3-dicarbonyl compounds. The dendritic organocatalysts show unprecedented recyclability with reproducible activity and enantioselectivity.