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. 2022 Mar 15;7(12):10649-10659.
doi: 10.1021/acsomega.2c00293. eCollection 2022 Mar 29.

An Efficient and Versatile Deep Eutectic Solvent-Mediated Green Method for the Synthesis of Functionalized Coumarins

Ishfaq Ahmad Rather  1 , Rashid Ali  1
Affiliations

An Efficient and Versatile Deep Eutectic Solvent-Mediated Green Method for the Synthesis of Functionalized Coumarins

Ishfaq Ahmad Rather et al. ACS Omega. .

Abstract

Herein, we report a green and efficient synthetic route for the construction of diverse functionalized coumarins in good-to-excellent yields (60-98%) via the Pechmann condensation. The optimized synthetic route involves a biodegradable, reusable, and inexpensive deep eutectic solvent (DES) of choline chloride and l-(+)-tartaric acid in a ratio of 1:2 at 110 °C. Interestingly, phloroglucinol and ethyl acetoacetate, upon reaction, furnished the functionalized coumarin (20) in 98% yield within 10 min. On the other front, the same DES at relatively lower reaction temperature (90 °C) was found to provide the bis-coumarins in decent yields (81-97%) within 20-45 min. Moreover, this particular method was found to be quite effective for large-scale coumarin synthesis without noteworthy reduction in the yields of the desired products. Noticeably, in this versatile approach, the DES plays a dual role as solvent as well as catalyst, and it was effectively recycled and reused four times with no significant drop-down in the yield of the product.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
Diverse functionalized coumarins (1–7) of therapeutic significance.
Figure 2
Figure 2
Bar graph showing the recyclability of ChCl/l-(+)-TA (1:2) for the construction of 7-hydroxy-4-methylcoumarin (10).
Scheme 1
Scheme 1. Synthesis of Diverse Bis-coumarin Derivatives (41–44) Using ChCl/l-(+)-TA (1:2)
Scheme 2
Scheme 2. Competitive Reactions for the Formation of Functionalized Coumarins in ChCl/l-(+)-TA (1:2) Based DES
Scheme 3
Scheme 3. Plausible Mechanism of the Formation of 7-Hydroxy-4-methylcoumarin (10) via DES of ChCl/l-(+)-TA (1:2)
See this image and copyright information in PMC

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