An Economical, Sustainable Pathway to Indole-Containing Oxindoles: Iron-Catalyzed 1,6-Conjugate Addition in Glycerol

Lan Tan,Abdul Rahman

doi:10.3390/su10082922

Abstract

The search for economical, sustainable and practical pathways in synthetic science would contribute to improving resource efficiency, developing a recycling economy and driving new-type urbanization. Green synthesis has established firm ground providing the right green yardstick for development of a sustainable approach to bioactive high-added value molecules and drug discovery, and further development of sustainable manufacturing processes in the pharmaceutical industry toward a green resource efficient economy. In this study, the combination of FeCl3 and glycerol exhibits a versatile and high catalytic activity in the atom economical 1,6-conjugated addition of para-quinone methides derived from isatins with indoles using the right green yardstick. The sustainable pathway provides the preparation of bioactive indole-containing oxindoles in excellent yields with superior advantages, such as the ready availability, low price and environmentally benign character of iron catalysis, easy product separation, cheap and safe bio-renewable glycerol as a green solvent, and catalytic system recycling under mild conditions.

Highlights

Resource efficiency is the maximising of the supply of funds, materials, staff, and other assets in order to function effectively in a sustainable manner, with minimum wasted resource expenses to minimise environmental impact [1]
The 1,6-conjugated addition reaction catalyzed by Brønsted acids or Lewis acids for new chemical bond formation can provide a variety of bioactive compounds, and has complete atom economy [11]
We report a highly efficient FeCl3 dissolved in glycerol catalyzed 1,6-conjugated addition reaction of para-quinone methides derived from isatins with indoles to afford bioactive indole-containing oxindoles in excellent yields

Summary

Introduction

Resource efficiency is the maximising of the supply of funds, materials, staff, and other assets in order to function effectively in a sustainable manner, with minimum wasted resource expenses to minimise environmental impact [1]. In today’s environment, the demand for the production of high-quality products with minimum waste and energy demands is a very important challenge to the coordinated development of new urbanization and employment growth via the economic analysis of resource efficiency policies [2,3]. Developing sustainable and practical pathways will be a long-term concerted and challenging task for scientists. In this regard, the 1,6-conjugated addition reaction catalyzed by Brønsted acids or Lewis acids for new chemical bond formation can provide a variety of bioactive compounds, and has complete atom economy [11]. The 1,6-conjugated addition reaction is attracting much research interest in academia [12,13,14]

Methods

Results

Conclusion