Microwave-Assisted Three-Component “Catalyst and Solvent-Free” Green Protocol: A Highly Efficient and Clean One-Pot Synthesis of Tetrahydrobenzo[b]pyrans

Sougata Santra,Alakananda Hajra,Anupam Roy,Adinath Majee,Matiur Rahman

doi:10.1155/2014/851924

Sougata Santra, Alakananda Hajra + Show 3 more

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https://doi.org/10.1155/2014/851924

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Journal: Organic Chemistry International	Publication Date: Sep 17, 2014
Citations: 54	License type: CC BY 3.0

Affiliation: Visva-Bharati University

Abstract

A green and highly efficient method has been developed for the one-pot synthesis of tetrahydrobenzo[b]pyrans via a three-component condensation of aldehydes, 1,3-cyclic diketones, and malononitrile under MW irradiation without using any catalyst and solvent. This transformation presumably occurs by a sequential Knoevenagel condensation, Michael addition, and intramolecular cyclization. Operational simplicity, solvent and catalyst-free conditions, the compatibility with various functional groups, nonchromatographic purification technique, and high yields are the notable advantages of this procedure.

Highlights

Development of environmentally benign and clean synthetic procedures has become the goal of organic synthesis in recent times [1,2,3,4,5]
The concept of environmental factor (E-factor) and atom economy have gradually become included into conventional organic synthesis in both industry and academia
As a part of our ongoing research to provide greener methodologies under solvent and catalyst-free conditions [27, 29, 68,69,70,71] we have found that the three-component condensation of aldehyde, 1,3-cyclic diketone, and malononitrile under MW irradiation without using any catalyst and solvent produced 4H-benzo[b]pyran derivatives in high yields within short reaction times (Scheme 1)

Summary

Introduction

Development of environmentally benign and clean synthetic procedures has become the goal of organic synthesis in recent times [1,2,3,4,5]. The multicomponent reactions (MCRs) are one of the most powerful and efficient tools in organic synthesis for the invention of biologically important scaffolds in the viewpoint of green chemistry [6,7,8,9]. Solvents are the main reason for an insufficient E-factor, especially in synthesis of fine chemicals and pharmaceutical industries [14, 15]. As a result, it has become imperative both in academia and industry to design catalystand solvent-free MCRs, as these processes are rendered green with reduction of waste, time, manpower, and cost [16,17,18,19,20,21]

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