Lossen rearrangement

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Lossen rearrangement
Named after Wilhelm Lossen
Reaction type Rearrangement reaction
Identifiers
RSC ontology ID RXNO:0000156

The Lossen rearrangement is the conversion of an acyl hydroxamate to an isocyanate and carboxylic acid side product. [1] [2] [3] [4] The isocyanate can be used further to generate ureas in the presence of amines or generate amines in the presence of H2O.

General reaction scheme for the Lossen rearrangement. Lossen-scheme.svg
General reaction scheme for the Lossen rearrangement.

Reaction mechanism

The acyl hydroxamate is first converted to its conjugate base. A concerted rearrangement event then occurs in which the amide substituent migrates to the amide nitrogen, the nitrogen donates a pair of electrons to form the isocyanate C=N double bond, and the N–O σ-bond breaks.

Arrow pushing mechanism for the Lossen rearrangement. Lossen-mech.svg
Arrow pushing mechanism for the Lossen rearrangement.

Historical references

See also

References

  1. ↑ Wang, Zerong (2010). Comprehensive organic name reactions and reagents. John Wiley & Sons, Inc. pp. 1772–1776. ISBN   9780471704508.
  2. ↑ Yale, H. L. (1943). "The Hydroxamic Acids". Chem. Rev. 33 (3): 209–256. doi:10.1021/cr60106a002.
  3. ↑ Bauer, L.; Exner, O. (1974). "The Chemistry of Hydroxamic Acids and N-Hydroxyimides". Angew. Chem. Int. Ed. Engl. 13 (6): 376. doi:10.1002/anie.197403761.
  4. ↑ Shioiri, Takayuki (1991). "Degradation Reactions". Comprehensive Organic Synthesis. 6: 795–828. doi:10.1016/B978-0-08-052349-1.00172-4. ISBN   9780080359298.
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