4-{(E)-[(3-fluorophenyl)imino]methyl}phenol

4-{(E)-[(3-Fluorophenyl)imino]methyl}phenol is a structurally related impurity of Ezetimibe, featuring a para-hydroxybenzyl moiety conjugated to a 3-fluorophenylimino group via a trans (E)-configured carbon-nitrogen double bond. The compound incorporates an electron-withdrawing fluorine substituent and a phenolic hydroxyl group, contributing to its distinct physicochemical profile compared to the parent drug. Its imino functionality arises from a synthetic side reaction during Ezetimibe production, likely via condensation of 3-fluorobenzaldehyde with the corresponding phenolic amine. This impurity serves as an HPLC reference standard for quantifying process-derived impurities in Ezetimibe active pharmaceutical ingredients.