First report of the application of simple molecular complexes as organo-catalysts for Knoevenagel condensation

Abstract

A series of molecular complex have been designed, synthesized and used as organo-catalyst for the first time for very efficient 10 Knoevenagel condensation. Molecular complexes are thermally stable, low cost for preparation, easily recyclable. Role of acidic proton in molecular complexes towards Knoevenagel condensation has been identified as the key factor and helps us to provide useful information of reaction path way. The acidic proton of catalyst enhances the electrophilicity of the aldehyde and accelerates dehydration process of reaction at room temperature (RT). Eco-friendly, green synthetic protocol for Knoevenagel condensation is used to synthesize a series of important cyano group containing synthetic precursor for synthesis of biologically active molecules at RT using minimum 15 amount of catalyst (~5 mol %) without chromatographic separation technique. Detailed mechanistic studies and substituents effect of aromatic aldehyde on reaction have been investigated. In addition biologically active 2-Amino-4H-Chromene derivatives have also been synthesized by Knoevenagel condensation of salicylic aldehydes with active methylene compounds, followed by intramolecular cyclization (via Michael addition) delivering higher yield within shortest reaction time at RT without any need of chromatographic separation.

Photocatalytic aerobic oxidative functionalization (PAOF) reaction of benzyl alcohols by GO-MIL-100(Fe) composite in glycerol/K2CO3 deep eutectic solvent

“…After completion of the reaction, the products were purified by re-crystallization. All the products were characterized by a comparison of their spectral data/melting points with the previously published works in the literature 37 , 38 .…”

Reactivity of hydrogen-bonded complexes of water, methanol, phenol and methyl amine

“…98 Substituted phenol dimers can be used as catalysts in Knoevenagel condensation. 111 In the next stage we turned to the consideration of mixed complexes of phenol with methanol. In these complexes phenol relative to methanol can act both as a proton donor and as a proton acceptor.…”

DABCO-catalyzed Knoevenagel condensation of aldehydes with ethyl cyanoacetate using hydroxy ionic liquid as a promoter

“… 1 Owing to the fact that the α,β-unsaturated carbonyl compounds produced by Knoevenagel reaction can further be used in the synthesis of fine chemicals, 2 therapeutic drugs, 3 natural products 4 and functional polymers, 5 research on this reaction has been a hot topic in organic synthesis. In recent years, a large number of catalytic systems were developed for this reaction and various new catalysts such as functionalized MOFs, 6 functionalized fibers, 7 simple molecular complexes, 8 C 3 N 4 , 9 cage, 10 copper powder, 11 zeolites, 12 enzymes, 13 polymers, 14 bovine serum albumin, 15 magnetic nanoparticles, 16 graphene oxide 17 and ammonium salts 18 have been employed to catalyze this reaction, each affording variable yields of Knoevenagel condensation compounds. However, even for the most favorable systems, this reaction often suffers from expensive catalysts, laborious work-up procedures, long reaction times and use of organic solvents or toxic metals.…”