8.3.4 Lossen Rearrangement

Ester of hydroxamic acid reacts with base to give isocyanate that could be converted into amine as shown in Hofmann rearrangement.

Mechanism

Examples:

All these four rearrangements have common intermediate isocyanate forming from different substrate precursors. Among the all, the Hofmann rearrangement is more convenient providing that other functional group do not react under the conditions.