1-azido-3-(bromomethyl)-5-ethynylbenzene is a trifunctional building block for chemical probe synthesis, typically employed for photoaffinity labeling in chemcial biology and medicinal chemistry. It contains a light-activated arylazide (photoreactive group), terminal alkyne tag (clickable handle), and bromine synthetic handle (connectivity group). When appended to a ligand or pharmacophore through its brominated linker, this probe building block allows for UV light-induced covalent modification of a biological target with potential for downstream applications via the alkyne tag.
Design of dantrolene-derived probes for radioisotope-free photoaffinity labeling of proteins involved in the physiological Ca2+ release from sarcoplasmic reticulum of skeletal muscle. 
Tandem photoaffinity labeling–bioorthogonal conjugation in medicinal chemistry.
Development of Sulfonamide Photoaffinity Inhibitors for Probing Cellular γ-Secretase.