Synthesis and Mesomorphic Behavior of a Vanillin-Derived Isoxazoline Bearing a Cyclic Carbonate Unit

Cyclic carbonate-based liquid-crystalline materials are attractive for ion-conductive media in lithium battery electrolytes.¹ Isoxazolines have also been explored as scaffolds for the design of compounds with liquid-crystalline properties.² Herein, a new vanillin-derived isoxazoline containing a cyclic carbonate moiety was synthesized through a five-step sequence involving alkylation, Steglich esterification, oxime formation, and 1,3-dipolar cycloaddition. The target compound, 2-methoxy-4-(5-(2-oxo-1,3-dioxolan-4-yl)-4,5-dihydroisoxazol-3-yl)phenyl 4-(decyloxy)benzoate, was obtained in 60% yield in the final step and characterized by 1D/2D NMR and FTIR. Mesomorphic behavior was investigated by DSC and POM. Upon heating, the compound showed a direct crystal-to-isotropic transition at 153 °C, whereas cooling revealed a monotropic mesophase at 120 °C, assigned as smectic based on focal-conic defects, followed by crystallization near 97 °C. Overall, the mesomorphic behavior of the target compound highlights structural features relevant to the design of ion-conductive liquid-crystalline materials with potential application on lithium battery electrolytes.