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

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

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.

PMID:35382332 | PMC:PMC8973037 | DOI:10.1021/acsomega.2c00293

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