|Title||Solvent-Induced Reversal of Activities between Two Closely Related Heterogeneous Catalysts in the Aldol Reaction|
|Publication Type||Journal Article|
|Year of Publication||2013|
|Authors||Kandel, K, Althaus, SM, Peeraphatdit, C, Kobayashi, T, Trewyn, BG, Pruski, M, Slowing, II|
|Type of Article||Article|
|Keywords||acid, aldol condensation, asymmetric aldol, c-13 nmr, condensation-reactions, enamine catalysis, iminium catalysis, mesoporous silica, Mesoporous silica nanoparticles, primary amine catalysts, proline, solid-state, solid-state nmr, solvent effects, water|
The relative rates of the aldol reaction catalyzed by supported primary and secondary amines can be inverted by 2 orders of magnitude, depending on the use of hexane or water as a solvent. Our analyses suggest that this dramatic shift in the catalytic behavior of the supported amines does not involve differences in reaction mechanism, but is caused by activation of imine to enamine equilibria and stabilization of iminium species. The effects of solvent polarity and acidity were found to be important to the performance of the catalytic reaction. This study highlights the critical role of solvent in multicomponent heterogeneous catalytic processes.
|Custom 1|| |