Used as a Wittig reagent precursor in organic synthesis to introduce photolabile 2-nitrobenzylidene protecting groups. The phosphonium salt is deprotonated to form an ylide that reacts with aldehydes or ketones, forming carbon-carbon double bonds that protect functional groups such as alcohols (via acetals), carboxylic acids, and others. Upon UV light exposure, the 2-nitrobenzyl group undergoes photolysis, enabling controlled release with spatial and temporal precision. This is valuable in light-triggered drug delivery systems, synthesis of complex biomolecules, solid-phase peptide synthesis, and preparation of caged compounds for biological studies.