Alkyl-, vinyl-, and aryl-substituted acyl azides undergo thermal 1,2-carbon-to-nitrogen migration with extrusion of dinitrogen — the Curtius rearrangement — producing isocyanates. Reaction of the isocyanate products with nucleophiles, often in situ, provides carbamates, ureas, and other N-acyl derivatives. Alternatively, hydrolysis of the isocyanates leads to primary amines.