Diphenyl phosphoryl azide (DPPA) is widely used in organic synthesis, particularly in peptide coupling reactions. It serves as a reagent for converting carboxylic acids into acyl azides, which can then be rearranged to form isocyanates through the Curtius rearrangement. This makes it valuable in the synthesis of amines, ureas, and carbamates. DPPA is also employed in the preparation of heterocycles and in the modification of amino acids or peptides. Its ability to facilitate mild and efficient reactions makes it a preferred choice in pharmaceutical and biochemical research for constructing complex molecular structures. Additionally, it is utilized in polymer chemistry for cross-linking and functionalizing polymers.