Synthesis of protected amines from N-hydroxyphthalimide esters via Curtius rearrangement

An efficient and mild method to prepare carbamoyl azides from NHP (N-hydroxyphthalimide) esters and TMSN₃ was developed. The structure of carbamoyl azide was confirmed by the X-ray analysis. Corresponding carbamoyl azides were converted into carbamates for isolation. This methodology allows an efficient access to primary, secondary, tertiary alkyl and aryl carbamates. Mechanistic studies reveal that Curtius rearrangement is responsible for the generation of carbamoyl azides.