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.

中文翻译：

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新型，高效，农业废料源催化剂在克诺文塔格尔缩合反应中的应用

提出了一种绿色，经济，环保的芳香醛，水杨醛与活性亚甲基化合物（如丙二腈和梅德鲁姆酸）Knoevenagel缩合反应的方法，可分别合成苄基丙二腈和3-羧基香豆素衍生物。该反应是在没有外部碱的情况下，使用源自农业废物的绿色催化剂WENBA {Nilgiri Bark Ash的水提取物（桉树）}作为有效的天然催化介质进行的。WENBA是一种新型的，从生态废料中获得的，生态安全且廉价的绿色催化剂。合成的化合物苄基丙二腈和3-羧基香豆素（2-oxo-2 H-1-苯并吡喃骨架在医学化学中具有多种应用，可用于合成生物活性分子。因此，已经开发了用于合成这类有机分子的多种方法。但是，报告的某些方法与有害物质有关，并且对环境有毒。它们具有更长的反应时间，较差的收率以及最终分离出的化合物的较低纯度。尽管有许多方法可用于这种生物活性分子的合成，但仍需要开发更新的试剂，这些试剂可提供对环境友好的方案，温和的反应条件，廉价的催化剂和纯度高且纯度高的最终产物分离方法。