Montmorillonite KSF as an Inorganic, Water Stable, and Reusable Catalyst for the Knoevenagel Synthesis of Coumarin-3-carboxylic Acids

L-Proline as an efficient and reusable promoter for the synthesis of coumarins in ionic liquid

“…Highly efficient reactions have been reported, involving the condensation of salicylaldehydes with malonates in the presence of piperidine under microwave conditions (Bogdal, 1998), and the use of montmorillonite KSF (Bigi et al, 1999) which requires high temperature and long reaction time (100 °C, 24 h). Solid-phase syntheses of 3-alkoxycarbonylcoumarins (Watson and Christiansen, 1998) and 3-acetylcoumarin utilizing the polymer reagent (vanden Eynde and Rutot, 1999) were also reported; however, they are not so effective in terms of yield and purity of products or recyclability of the polymer reagent.…”

Classical Keggin Intercalated into Layered Double Hydroxides: Facile Preparation and Catalytic Efficiency in Knoevenagel Condensation Reactions

“…[41][42][43] Knoevenagel condensation is a base-catalyzed reaction. Initially, Knoevenagel condensation of benzaldehyde with ethyl cyanoacetate catalyzed by Mg3Al-PW12 has been carried out at 60 o C in mixed solution (Vi-propanol:Vwater = 2 : 1), during which an excellent yield of > 99.9% was obtained ( Table 2, Entry 1).…”

Indium Modified Mesoporous Zeolite AlMCM-41 as a Heterogeneous Catalyst for the Knoevenagel Condensation Reaction

“…An aqueous solution of sodium aluminate was added into tetraethylorthosilicate (TEOS) (19.3 gm) containing aqueous solution of cetyltrimethylammonium bromide (CTABr) (7.6 gm) and 10% aqueous tetramethylammonium hydroxide (TMAOH) (17 gm) was added with constant stirring at room temperature for 1 h. then the resulting mixture was treated with 2 N H2SO4 to adjust the pH 10 to 10.5. The resultant gel was transferred into autoclavable bottle at 100 o C for 96 h. The solid product was filtered, washed several times with distilled water, dried in air at 373 K and finally, calcined at 540 o C for 6 h. The calcined materials were converted into H-form by ion exchange with aqueous 1 M NH 4 Cl solution this procedure was repeated twice followed by calcination at o C for 8 h. Catalyst characterization. The X-ray powder diffraction patterns were recorded by using Bruker 8D X-ray diffractometer using CuKα radiation of wavelength = 1.54056 Aº.…”

“…2 In addition to that this reaction has been used widely for the preparation of coumarin derivatives, which are very important intermediates in cosmetics, perfumes and pharmaceuticals industry. 3 Many alternative methodologies and reagents were developed for Knoevenagel reaction, such as clays, 4 layered double hydroxides (LDHs), 5 hydrotalcites, 6 piperidine 7 or amino acids such as glycine, alanine, L-proline 8 and guanidine. 9 In addition to these methods, in recent years, various homogenous and heterogeneous catalyst are used, such as TiCl4, 10 ZnCl2, 11 MgF2,12 CeCl3.…”