Isocyantes ureas

Isocyantes and their rimple reaction products have been known since 1849 when Wurtz synthesized the first isocyanate. The great reactivity of the isocyanate was recognized when the correspcmding ureas were formed by reaction with amines. 

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

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