TheKnoevenagel Condensation

Abstract

Knoevenagel's first papers in this field were concerned with the condensation of formaldehyde with diethyl malonate and with ethyl benzoylacetate. The catalyst was ethylamine. A number of other aldehydes were reported to condense similarly with diethyl malonate, ethyl benzoylacetate, ethyl benzoylpyruvate, and acetylacetone under the influence of various primary and secondary amines. In 1896, Knoevenagel reported benzaldehyde with ethyl aceoacetate condensed at room temperature in the presence of piperdine to give a bis compound, but that when the reaction was run in a freezing mixture, the product was acetoacetate. For the purposes of this chapter, the Knoevenagel condensation is defined as the reaction between an aldehyde or ketone or any compound having an active methylene group, brought about by an organic base or ammonia and their salts.

One-pot synthesis of hierarchical porous layered hybrid materials based on aluminosilicate sheets and organic functional pillars

“…58,59,60,61,62 In this work, it is analyzed the catalytic activity of the more accessible LHM-TEMS-H hybrid material, after the protonic exchange, to perform condensation reactions. In this way, the presence of compensating sodium cations which could act as base catalytic centers is avoided.…”

Magnetically Separable Base Catalysts: Heterogeneous Catalysis vs. Quasi-Homogeneous Catalysis

“…The condensations of activated methylene groups with aldehydes, in particular Knoevenagel [36] and nitroaldol [37] condensations, are efficient carbon-carbon bond forming reactions. These reactions are utilized widely in the synthesis of valuable organic compounds that are of importance to different biological and pharmaceutical applications.…”

Preparation and Optical Properties of Novel 3-Alkoxycarbonyl Aza- and Diazacoumarins

“…The first one involves condensation of salicylic aldehydes with malonic acids or derivatives giving the 3-carboxylic acids (or derivatives) that may successively undergo decarboxylation. [20] The reaction is catalyzed by weak bases. The Knoevenagel condensation was used by Bredereck et al [13] to prepare 3-ethoxycarbonyl-5-hydroxy-7-methyl-6,8-diazacoumarin 1 and later by Moffett [21] to produce 3-carboxy-5-azacoumarin 2 (Scheme 1).…”