Novel ionic liquid dihydrogen 4,4′-trimethylenedipiperidine phosphate-catalyzed greener and efficient synthesis of dihydro pyrano [2,3-c] pyrazole

• Published in: Research on chemical intermediates 2023-03, Vol.49 (3), p.819-835
• Main Authors: Tanpure, Sagar, Mulik, Abhijeet, Rajmane, Mohan, Lawande, Shamrao
• Format: Article
• Language: English
• Subjects: Aldehydes; Catalysis; Catalysts; Chemical synthesis; Chemistry; Chemistry and Materials Science; Column chromatography; Hydrazines; Inorganic Chemistry; Ionic liquids; Malononitrile; NMR; Nuclear magnetic resonance; Phosphoric acid; Physical Chemistry; Pyrazole; Room temperature
• ISSN: 0922-6168; 1568-5675
• DOI: 10.1007/s11164-022-04904-5

A novel robust acidic ionic liquid dihydrogen 4,4′-trimethylenedipiperidine phosphate was synthesised from 4, 4′-trimethylenedipiperidine and phosphoric acid. The prepared catalyst was characterized by FTIR, 1 H-NMR, 13 C NMR and mass spectroscopy. The synthesized novel catalyst was found to be competent for synthesis of pyranopyrazole derivatives through one-pot multicomponent condensation of diverse aryl aldehydes with malononitrile, ethyl acetoacetate and hydrazine hydrate in the presence of a catalytic amount of dihydrogen 4,4′-trimethylenedipiperidine phosphate [H 2 -TMDP][HPO 4 ] as an efficient and inexpensive catalyst at room temperature. The novel catalyst proved to be rapid and efficient for synthesis of pyranopyrazole derivatives attributing to excellent yields of 86–92% within 12–16 min. Merits of this meticulously designed protocol are the use of novel ionic liquid, easy work-up process, good to excellent yields, short reaction time and purification without column chromatography. Graphical abstract