Solvent-free synthesis of 4-substituted coumarins catalyzed by novel brønsted acidic ionic liquids with perchlorate anion: a convenient and practical complementary method for pechmann condensation

• Published in: Reaction kinetics, mechanisms and catalysis Vol. 133; no. 1; pp. 383 - 403
• Main Authors: Taib, Layla Ahmed, Keshavarz, Mosadegh, Parhami, Abolfath
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 2021
• Subjects: Catalysis; Chemistry; Chemistry and Materials Science; Industrial Chemistry/Chemical Engineering; Physical Chemistry; PipBs; ClO; ); IL catalysts; PhBs; Coumarin; Bails; Pechmann condensation
• ISSN: 1878-5190; 1878-5204
• DOI: 10.1007/s11144-021-01941-w

Herein, three novel sulfonic-functionalized Brønsted acidic ionic liquids containing perchlorate anion counterparts were prepared and well characterized using FTIR,
1
H and
13
C NMR, Electro-Spray Ionization Mass Spectrometry (ESI-MS), elemental analysis (CHNS) and TG techniques. These ionic liquid catalysts were prepared through simple and ecofriendly procedures and then applied as efficient catalysts with high yields under solvent-free conditions for the synthesis of 4-substituted coumarins through the Pechmann condensation of different phenols and
β
-ketoesters. Compared to previous works, the proposed method offers several benefits, such as cleaner reactions, decreased reaction times, high yields, and the lack of laborious workup or purification procedures. Particularly, these catalysts make the condensation of less activated phenols feasible. Besides the described benefits, this advanced protocol was applied successfully for the synthesis of coumarins from γ-lactones such as 3-acetyldihydrofuran-2(3
H
)-one. The simplicity in operation, applicability and feasibility of this protocol for diverse substrates make it an efficient alternative to conventional methods.
Graphic abstract