4-Bromo-2-hydroxybenzaldehyde is a bifunctional aromatic building block featuring a bromine atom, a hydroxyl group, and an aldehyde group on a benzene ring. Its molecular formula is C7H5BrO2, with a molecular weight of 201.02 g/mol. The compound exists as a solid at room temperature and is commonly used in organic synthesis. This compound serves as a versatile intermediate in the preparation of pharmaceuticals, agrochemicals, and fine chemicals. The aldehyde group allows for condensation reactions (e.g., Schiff base formation), while the bromine atom enables cross-coupling reactions such as Suzuki or Heck couplings. The hydroxyl group can be further functionalized via etherification or esterification. In medicinal chemistry, it is frequently employed as a key fragment for constructing heterocyclic compounds, including benzoxazoles and salicylaldehyde derivatives, which are relevant to drug discovery efforts targeting neurological and inflammatory diseases. Due to its reactive sites, 4-bromo-2-hydroxybenzaldehyde is also utilized in the synthesis of ligands for metal complexes and as a precursor for fluorescent probes. It should be stored under inert atmosphere and protected from light to prevent degradation.