Lossen rearrangement
{{Short description|Chemical rearrangement reaction}}
{{Use dmy dates|date=April 2023}}
{{Reactionbox
| Name = Lossen rearrangement
| Type = Rearrangement reaction
| NamedAfter = Wilhelm Lossen
| Section3 = {{Reactionbox Identifiers
| RSC_ontology_id = 0000156
}}
}}
The Lossen rearrangement is the conversion of a hydroxamate ester to an isocyanate. Typically O-acyl, sulfonyl, or phosphoryl O-derivative are employed.{{cite book |last1=Wang |first1=Zerong |title=Comprehensive organic name reactions and reagents |date=2010 |publisher=John Wiley & Sons, Inc. |isbn=9780471704508 |pages=1772–1776}}{{cite journal|author=Yale, H. L. |journal=Chem. Rev.|year=1943|volume=33|pages= 209–256|doi=10.1021/cr60106a002|title=The Hydroxamic Acids|issue=3}}{{cite journal|author1=Bauer, L. |author2=Exner, O. |journal=Angew. Chem. Int. Ed. Engl.|year=1974|volume=13|pages= 376|doi=10.1002/anie.197403761|title=The Chemistry of Hydroxamic Acids and N-Hydroxyimides|issue=6}}{{cite journal|last1=Shioiri|first1=Takayuki|title=Degradation Reactions|journal=Comprehensive Organic Synthesis|date=1991|volume=6|pages=795–828|isbn=9780080359298|doi=10.1016/B978-0-08-052349-1.00172-4}} The isocyanate can be used further to generate ureas in the presence of amines or generate amines in the presence of H2O.
Reaction mechanism
The mechanism below begins with an O-acylated hydroxamic acid derivative that is treated with base to form an isocyanate that generates an amine and CO2 gas in the presence of H2O. The hydroxamic acid derivative is first converted to its conjugate base by abstraction of a hydrogen by a base. Spontaneous rearrangement releases a carboxylate anion to produce the isocyanate intermediate. The isocyanate is then hydrolyzed in the presence of H2O. Finally, the respective amine and CO2 are generated by abstraction of a proton with a base and decarboxylation.
Image:Lossen-rearrangement.svg
Hydroxamic acids are commonly synthesized from their corresponding esters.{{cite journal|last1=Hauser|first1=C. R.|last2=Renfrow, Jr..|first2=W. B.|title=Benzohydroxamic Acid|journal=Organic Syntheses|date=1939|volume=19|pages=15|doi=10.15227/orgsyn.019.0015}}
Historical references
- {{cite journal|last1=Lossen|first1=W.|title=Ueber Benzoylderivate des Hydroxylamins|journal=Justus Liebigs Annalen der Chemie|date=1872|volume=161|issue=2–3|pages=347–362|doi=10.1002/jlac.18721610219|url=https://zenodo.org/record/1427305}}
- {{cite journal|last1=Lossen|first1=W.|title=Ueber die Structurformel des Hydroxylamins und seiner amidartigen Derivate|journal=Justus Liebigs Annalen der Chemie|date=1875|volume=175|issue=3|pages=271–304|doi=10.1002/jlac.18751750303|url=https://zenodo.org/record/1427343}}
- {{cite journal|last1=Lossen|first1=W.|title=Methode, die Carboxylgruppe aromatischer Säuren durch die Amidgruppe zu ersetzen|journal=Justus Liebigs Annalen der Chemie|date=1875|volume=175|issue=3|pages=313–325|doi=10.1002/jlac.18751750305|url=https://zenodo.org/record/1427345}}
See also
References
{{Reflist}}
External links
- {{cite web | url = https://www.youtube.com/watch?v=0-hbqMzgxw0 | title = Mechanism in Motion: Lossen rearrangement| date = 7 October 2010| via = YouTube}}