Dimethyl (1-diazo-2-oxopropyl)phosphonate, commonly known as the Ohira-Bestmann reagent, is a versatile organophosphorus compound used in organic synthesis. It is primarily employed for the homologation of aldehydes to terminal alkynes through a modified Seyferth-Gilbert reaction mechanism, providing a mild and efficient method for alkyne synthesis. Additionally, it facilitates Horner-Wadsworth-Emmons (HWE) reactions, converting aldehydes and ketones into α,β-unsaturated esters or ketones with high E-selectivity and stereocontrol in carbon-carbon double bond formation. The diazo functionality supports metal-catalyzed carbene insertions, including C-H activations and cyclopropanations of alkenes, which are valuable for building complex frameworks in pharmaceutical, agrochemical, and natural product synthesis. Due to its inherent reactivity and potential for explosive decomposition, it requires careful handling, storage under inert atmosphere, and avoidance of heat, shock, or light exposure.