Bio‐Based Deep Eutectic Solvent for Catalyst‐Free Synthesis of Xanthenediones

ABSTRACT We developed an environmentally friendly and efficient method for preparing xanthenedione derivatives via a multicomponent Knoevenagel–Michael cyclocondensation reaction in a bio‐based deep eutectic solvent (DES). The reaction combined aromatic or heteroaromatic aldehydes with dimedone in a DES prepared from lactic acid, maltose, and amla juice at room temperature without an added catalyst. Among the DES systems tested, a 3:1:3 mixture of lactic acid, maltose, and amla juice performed best, yielding xanthenedione derivatives in 64%–98% yields within 1–5 h. The method accommodated aldehydes bearing electron‐donating and electron‐withdrawing groups, as well as selected heteroaromatic aldehydes. Mechanistic considerations suggest that the DES activates the aldehyde and promotes dimedone enolization through hydrogen bonding and acidity, facilitating Knoevenagel condensation, Michael addition, and cyclodehydration. The DES was reused for five cycles, although its efficiency gradually decreased. Fourier‐transform infrared (FT‐IR) and proton nuclear magnetic resonance ( 1 H NMR) analysis after the fifth cycle showed that the DES retained its main spectral features. Green chemistry metrics, including atom economy, the E‐factor, reaction mass efficiency, and process mass intensity, support the sustainability of this approach. Overall, this study demonstrates that bio‐based DES systems can serve as recyclable solvents and catalytic media for multicomponent organic synthesis.