A More Sustainable and Greener Process for Preparing 3,4,5‐Trisubstituted Furan‐2‐one Derivatives

Abstract

Treatment of 4,4′‐trimethylenedipiperidine with two equivalents of glacial acetic acid gave a cream‐like liquid with a pale yellow color. Then, its ionic chemical structure was demonstrated by different spectroscopic techniques. The thermal behavior of the new ionic liquid was also studied by TGA/DTA and DSC techniques to record its phase transitions and thermal stability and compare those with another analog, i. e., 1H,4H‐piperazine‐N,N′‐diium diacetate. Then, the multicomponent condensation of halogen‐substituted benzaldehydes with dimethyl 2‐(phenylamino) fumarate was investigated using the new ionic liquid in ethanol, an eco‐friendly medium. Excellent yield with 100 % conversion was obtained and pure products could be isolated directly from ethanol. After separating pure products, the residue solution was employed in the next run without separation, concentration, purification, or activation. Furthermore, the synthesis of methyl 2‐(4‐chlorophenyl)‐5‐oxo‐4‐(phenylamino)‐2,5‐dihydro‐furan‐3‐carboxylate was carried out on a large scale using the current catalytic process, affording a conversion of 100 % and a high yield of the crystalline product even after ten consecutive runs. Energy efficiency, cost‐ and time‐saving, and waste prevention demonstrate the newly developed metal‐ and halogen‐free catalysis as a more sustainable catalytic process for preparing 3,4,5‐trisubstituted furan‐2‐one derivatives on the laboratory and industrial scale.