Use of Immobilized Organic Base Catalysts for Continuous-Flow Fine Chemical Synthesis

A continuous-flow two-step process for the production of multifunctional intermediate compounds was performed with a combination of two column reactors packed with different organic immobilized catalysts. The first step of the reaction, nitroaldol condensation between aromatic aldehydes and nitromethane, is promoted by a silica gel-supported primary amine; the second step, Michael addition of β-dicarbonyl compounds to the nitrostyrenes obtained in the first step, is catalyzed by a silica gel-supported guanidine TBD. In both cases, the catalysts can be directly reused for several runs with no significant changes in activity.