Abstract

We revealed a catalyst-free, green and rapid one-pot four-component tandem strategy for the preparation of dihydropyrano[2,3-c]pyrazoles – a biologically significant scaffold – via Knoevenagel-Michael cyclocondensation based on green chemistry principles. Highlights of the current practice are the application of non-hazardous reaction circumstances, catalyst-free, operational simplicity, use of inexpensive initiating substances, isolation of pure product via easy filtration thus preventing the requirement for column chromatography, metal-free, excellent yields, time-saving aspects of the reaction. However, the green ethylene glycol (E-G) can be recycled at least six times with no considerable reduction in activity making it greatly advantageous in addressing the industrial requirements and environmental worries.

Graphic Abstract

The catalyst-free and environmentally friendly synthesis of dihydropyrano[2,3-c]pyrazole scaffolds are reported via ethylene glycol (E-G) as a green, reusable and biodegradable promoting media via tandem Knoevenagel-Michael cyclocondensation reaction of ethyl acetoacetate, hydrazine hydrate/phenylhydrazine, aromatic/aliphatic aldehydes and malononitrile provided the anticipated products in outstanding yields and short reaction times which might solve some cost problems in industry

中文翻译：

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乙二醇（EG）辅助的可重用和可生物降解的溶剂介质，无催化剂的绿色合成二氢吡喃并[2,3-c]吡唑支架

摘要

我们发现无催化剂，绿色和快速一锅四部分串联的二氢吡喃并[2,3-的准备策略Ç ]吡唑-生物显著支架-通过Knoevenagel反应，迈克尔环合基于绿色化学原则。当前实践的重点是在无害反应条件下的应用，无催化剂，操作简便，使用廉价的引发剂，通过分离纯产物易于过滤，从而避免了对柱色谱法的需求，无金属，优异的收率，节省了反应时间。但是，绿色乙二醇（EG）可以循环使用至少六次，而活性不会显着降低，这使其在满足工业要求和环境问题方面具有极大优势。

图形摘要

的二氢吡喃的和环境友好的无催化剂的合成[2,3- c ^ ]吡唑支架报告通过乙二醇（EG），为绿色，可重复使用的和可生物降解促进媒体经由乙酰乙酸乙酯，水合肼/的串联的Knoevenagel -迈克尔反应环化缩合苯肼，芳香族/脂肪族醛和丙二腈提供了预期的产品，具有出色的收率和较短的反应时间，这可能解决了工业上的一些成本问题