Novel 1,2,3-triazolium-tagged proline derivatives were synthesized by copper-catalyzed click-reaction of alkynes with azides and N-alkylation of the resulting 1,2,3-triazoles. They were applied as recyclable organocatalysts in direct asymmetric aldol and Michael reactions with high enantioselectivity and diastereoselectivity. These catalysts performed better than (S)-proline itself; that is to say
Hydroxy-α-amino acids modified by ionic liquid moieties: recoverable organocatalysts for asymmetric aldol reactions in the presence of water
作者:Dmitriy E. Siyutkin、Alexander S. Kucherenko、Sergei G. Zlotin
DOI:10.1016/j.tet.2008.12.045
日期:2009.2
or PF6 anions efficiently catalyze the asymmetric aldol reaction between aldehydes and ketones in the presence of water to generate aldols with high distereo- (up to 98:2) and enantioselectivity (up to >99% ee). 4-Hydroxyproline modified by the 4-(5-n-nonyl)-pyridinium hexafluorophosphate moiety retains its activity and selectivity over at least eight reaction cycles.