Indian Journal of Chemistry Vol. 59B, February 2020, pp. 258-270 Application of novel, efficient and agro-waste sourced catalyst for Knoevenagel condensation reaction K Kantharaju* & Prashant B Hiremath Peptide and Medicinal Chemistry Research Laboratory, Department of Chemistry, Rani Channamma University, P-B, NH-4, Belagavi 591 156, India E-mail: kk@rcub.ac.in Received 11 October 2018; accepted (revised) 15 November 2019 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. Keywords: Agro-waste, Knoevenagel reaction, Benzylidinemalononitrile, Coumarin-3-carboxylic acid, room temperature Environmental issues associated with many of the organic reactions have created a huge challenge for the researchers to establish eco-friendly, sustainable or greener approaches for the existing organic transformations 1,2 . The use of aqueous media instead of volatile organic solvents has got huge attention in organic reactions. Recently, eco-friendly, green and benign approaches have gained huge attention to carry out the organic transformation at ambient temperature. The use of hazardous reagents as catalysts during reaction seriously affects the human health and extremely damages to our environment. Nowadays, various water extract catalytic approaches have also given more attention due to its clean, simple, safe, economic and high yielding advantages 3 .These room temperature reactions being highly greener in their approach which strongly also fulfil the principles of ‘Green Chemistry’ 4 . Coumarin-3-carboxylic acid represents as a prominent heterocycle with wide variety of applications showed in biological activities and in material science. The reported literature reveals that, coumarin-3-carboxylic acids how potential effects in terms of medicinal application such as anti-coagulant 5 , anti-bacterial 6 , anti-inflammatory 7 , anti-HIV 8 and neuro protective agents 9 .They have also been employed as prominent intermediates for the synthesis of various pharmacologically potential compounds such as -lactams 10 , isoureas 11 and tetrahydropyridones 12 .The ester and amide derivatives ofcoumarin-3-carboxylic acids are well known for their efficient anti- cancer 13 properties which include the inhibition of tumour cell growth and invasion in vitro and in vivo 14 . The coumarin-3-carboxylic acids have not just focused to biological activities apart from that, they have also employed in triplet oxygen sensitizers 15 , cosmetics, perfume industries, pharmaceuticals 16 , also in the production of insecticide, optical brighteners 17 , as fluorescent probes 18 and laser dyes 19 . They have also been extensively used as a ligand in metal-coumarin preparation and showed prominent bio-applications 20,21 . The above mentioned and several other applications have gained promising importance, which has made coumarin-3-carboxylic acids as an important objective for the researchers. The previous reported method adopted the synthesis of CORE Metadata, citation and similar papers at core.ac.uk Provided by NOPR