Catalysis Letters, Vol.146, No.1, 212-219, 2016
Ion-Tagged Prolinamide Organocatalysts for the Direct Aldol Reaction On-Water
A concise synthesis of two imidazolium ion-tagged prolinamide organocatalysts 3 and 4, varying in anionic component (CF3COO- and PF6-, respectively) is presented. The latter could be classified as an ionic liquid with a melting point of 66.3 degrees C, and glass transition temperature of 14.5 degrees C. The efficiency of each catalyst was compared via a direct aldol reaction revealing a large contrast in catalytic performance, with the catalyst bearing the PF6- anion being superior. The optimal conditions were determined to be an on-water reaction system, and substrate scoping gave a range of desired aldol products in high conversion (up to >99 %), dr (up to 98:2), and er (up to 96:4). The application of these catalysts to beta-nitrostyrene conjugate addition is also presented. [GRAPHICS] .