(654c) Magnetic Superbasic Nano Catalysts for Rapid Catalyst Removal and Direct Product Isolation

Organosuperbases, such as the classic proton sponge (1,8)-bis(dimethylamino)naphthalene (DMAN) have become very important reagents in organic chemistry over the past years. Yet work-up such reactions remains challenging and tedious, particularly when using reagents of solubility similar to the desired products and a low tendency to crystallize. Thus, a chemically stable magnetic base with rapid capability for quantitative separation would be most interesting for industrial application and entail significant solvent savings, reduce time, expensive equipment and permit reagent reusability. Magnetic nanoparticles have fascinated scientists for several decades and were used in a plethora of applications. In chemical synthesis, magnetic nanoparticles have recently gained attraction for example in the field of catalysis since they combine high surface area with simple separation.

Here we present an organic superbase, coupled to magnetic nanoparticles, with stability amenable for use in challenging reaction conditions. We further show that such an easy-to-separate reagent is useful in a number of condensation reactions and simplifies work-up and product isolation The immobilized magnetic superbase reagent was tested in the base-catalyzed Knoevenagel and Claisen-Schmidt type condensations and showed conversions up to 99%. High yields up to 97 % of isolated product could be obtained by simple recrystallization without using column chromatography. Recycling of the catalyst was simple and fast with insignificant decrease in catalytic activity.

Schneider, E. M.; Raso, R. A.; Hofer, C. J.; Zeltner, M.; Stettler, R. D.; Hess, S. C.; Grass, R. N.; Stark, W. J. The Journal of Organic Chemistry 2014, 79, 10908