Batch and Flow Green Microwave‐Assisted Catalytic Conversion Of Levulinic Acid to Pyrrolidones

• Published in: ChemSusChem 2024-08, Vol.17 (15), p.e202301200-n/a
• Main Authors: Calcio Gaudino, Emanuela, Manzoli, Maela, Testa, Maria Luisa, La Parola, Valeria, Grillo, Giorgio, Cravotto, Giancarlo, Acciardo, Elisa, Tabasso, Silvia
• Format: Article
• Language: English
• Subjects: Amines; Bimetals; Catalytic converters; continuous flow process; CPME; Gold; Industrial applications; Levulinic acid; microwaves; Palladium; pyrrolidones; Solvents
• ISSN: 1864-5631; 1864-564X; 1864-564X
• DOI: 10.1002/cssc.202301200

This paper reports a new sustainable protocol for the microwave‐assisted catalytic conversion of levulinic acid into N‐substituted pyrrolidones over tailor‐made mono (Pd, Au) or bimetallic (PdAu) catalysts supported on either highly mesoporous silica (HMS) or titania‐doped HMS, exploiting the advantages of dielectric heating. MW‐assisted reductive aminations of levulinic acid with several amines were first optimized in batch mode under hydrogen pressure (5 bar) in solvent‐free conditions. Good‐to‐excellent yields were recorded at 150 °C in 90 min over the PdTiHMS and PdAuTiHMS, that proved recyclable and almost completely stable after six reaction cycles. Aiming to scale‐up this protocol, a MW‐assisted flow reactor was used in combination with different green solvents. Cyclopentyl methyl ether (CPME) provided a 99 % yield of N‐(4‐methoxyphenyl) pyrrolidin‐2‐one at 150 °C over PdTiHMS. The described MW‐assisted flow synthesis proves to be a safe procedure suitable for further industrial applications, while averting the use of toxic organic solvents. Microwave‐assisted batch and flow syntheses of pyrrolidones from levulinic acid have been exploited under neat conditions and using CPME as green solvent.