WEB: A green and an efficient catalyst for Knoevenagel condensation under grindstone method (original) (raw)
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2020
A greener, economic and eco-friendly method for Knoevenagel condensation of aromatic aldehyde, salicylaldehyde with active methylene compounds like malononitrile and Meldrum's acid to synthesize benzylidinemalononitrile and 3-carboxy coumarin derivatives respectively is demonstrated. The reaction has been carried out in the absence of external base using agro-waste sourced green catalyst WENBA {Water Extract of Nilgiri Bark Ash (Eucalyptus)} as an efficient natural catalytic medium. WENBA is a novel, ecologically safe and inexpensive green catalyst obtained from the agro-waste feedstock. The synthesized compounds benzylidinemalononitrile and 3-carboxy coumarin (2-oxo-2H-1-benzopyran) backbone have multiple applications in medicinal chemistry for the synthesis of bioactive molecules. Thus, a wide number of methodologies have been developed for the synthesis of this class of organic molecules. However, some of the methods reported are associated with hazardous materials and are toxic to the environment. They have longer reaction times, poor yields, and with lower purity of final isolated compound. In spite of a large number of methodologies available for this bioactive molecule synthesis, there is still demand for the development of newer reagents, which give environmentally friendly protocols, mild reaction conditions, inexpensive catalyst and final product isolation in pure form with good yields.
Catalysis Communications, 2006
A novel, efficient and eco-friendly MgO/ZrO 2 catalyst is put forward for the Knoevenagel condensation. The as synthesized catalyst MgO/ZrO 2 was characterized by elemental analysis, XRD, FTIR, particle size, SEM-EDXS, average pore diameter, BET surface area analysis, and thermal gravimetric analysis. The Knoevenagel condensation of several aldehydes with ethyl cyanoacetate and malononitrile was carried out at 60°C on MgO/ZrO 2 catalyst in the absence of solvent. .in (M.B. Gawande), rvjayaram @udct.org (R.V. Jayaram). www.elsevier.com/locate/catcom Catalysis Communications 7 (2006) 931-935
2019
A useful method for Knoevenagel condensation has been developed from the reaction between active methylene compound 1 and aldehyde 2 using the water extract of onion as a green catalyst. This method is suitable for variety of aldehydes including, substituted aromatic, aliphatic, α, β-unsaturated, and heterocyclic with malononitrile or ethyl cyanoacetate, and affords the α-cyanoacrylonitriles and α-cyanoacrylatesin excellent yields (Up to 98%). The products are isolated without column chromatography. The use of water extract of onion has several advantages such as low price, easy handling, simple work up procedure and environmentally benign.
Green Approach for Knoevenagel Condensation of Aromatic Aldehydes with Active Methylene Group
Synthetic Communications, 2012
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Jordan Journal of Chemistry, 2013
Sodium ascorbate (SA), acts as an efficient catalyst in the Knoevenagel condensation reaction of aryl aldehydes with Meldrum's acid in water as an environmental friendly solvent. In this reaction, 5-arylidene-2,2-dimethyl-1,3-dioxane-4,6-dione derivatives were obtained with high yields at shorter reaction periods at room temperature. The advantages of this method are simplicity, green, safe, convenient work-up, inexpensive and readily available catalyst.
Uncatalysed Knoevenagel condensation in aqueous medium at room temperature
Knoevenagel condensation of various aromatic and heteroaromatic aldehydes with active methylene compounds like malononitrile, ethyl cyanoacetamide, ethyl cyanoacetate, barbituric acids, MeldrumÕs acid, dimedone and pyrazolone proceeds smoothly with stirring in an aqueous medium. The reactions occur at room temperature giving excellent yields of the products. The work-up procedure is very simple and the products do not require further purification.
The green Knoevenagel condensation: solvent-free condensation of benzaldehydes
Green Chemistry Letters and Reviews
This paper presents a novel, green Knoevenagel procedure for the chemical transformation of benzaldehydes into their corresponding α,β-unsaturated acids. The essential part of this procedure is a solvent-free condensation which uses environmentally benign amines or ammonium salts as catalysts instead of pyridine and piperidine as used in the traditional Knoevenagel condensation. The condensation step is followed by a decarboxylation in the solid phase, resulting in high overall yields and purity. The influence of temperature and catalyst type on the yield of sinapinic acid was monitored for the reaction between syringaldehyde and malonic acid. After optimization of this reaction, its scope was explored for various types of benzaldehydes demonstrating a broad applicability of this procedure. The developed method provides good to an excellent conversion of various benzaldehydes and high selectivity to the respective α,β-unsaturated acids in an environmentally friendly and efficient way.
Simple and Solvent Free Knoevenagel Condensationby Using Gadolinium Oxide Catalyst
Journal of biological and chemical chronicles, 2019
INTRODUCTION: The Knoevenagel condensation is one of the important reaction in organic synthesis. In this reaction aromatic aldehydes were reacted with numerous active methylene groups like ethyl acetoacetate, malanonitrile, diethyl malonate etc. It shows number of applications in various areas like drugs, cosmetics, perfumes 1,2 , insecticides, herbicides, polymers 3-5. It has shown significant biological activities like ECG receptor, antiproliferative effects on keratinocytes 6. It is also useful in the synthesis of fine chemicals and various biologically active heterocyclic compounds.