Lossen rearrangement

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

The Lossen rearrangement is the conversion of a hydroxamate ester to an isocyanate. Typically O-acyl, sulfonyl, or phosphoryl O-derivative are employed.^[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.

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.

Hydroxamic acids are commonly synthesized from their corresponding esters.^[5]

Historical references

Lossen, W. (1872). "Ueber Benzoylderivate des Hydroxylamins". Justus Liebigs Annalen der Chemie. 161 (2–3): 347–362. doi:10.1002/jlac.18721610219.
Lossen, W. (1875). "Ueber die Structurformel des Hydroxylamins und seiner amidartigen Derivate". Justus Liebigs Annalen der Chemie. 175 (3): 271–304. doi:10.1002/jlac.18751750303.
Lossen, W. (1875). "Methode, die Carboxylgruppe aromatischer Säuren durch die Amidgruppe zu ersetzen". Justus Liebigs Annalen der Chemie. 175 (3): 313–325. doi:10.1002/jlac.18751750305.

References

^ Wang, Zerong (2010). Comprehensive organic name reactions and reagents. John Wiley & Sons, Inc. pp. 1772–1776. ISBN 9780471704508.
^ Yale, H. L. (1943). "The Hydroxamic Acids". Chem. Rev. 33 (3): 209–256. doi:10.1021/cr60106a002.
^ 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.
^ Shioiri, Takayuki (1991). "Degradation Reactions". Comprehensive Organic Synthesis. 6: 795–828. doi:10.1016/B978-0-08-052349-1.00172-4. ISBN 9780080359298.
^ Hauser, C. R.; Renfrow, Jr.., W. B. (1939). "Benzohydroxamic Acid". Organic Syntheses. 19: 15. doi:10.15227/orgsyn.019.0015.

External links

"Mechanism in Motion: Lossen rearrangement" – via YouTube.

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[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.

[5] Hauser, C. R.; Renfrow, Jr.., W. B. (1939). "Benzohydroxamic Acid". Organic Syntheses. 19: 15. doi:10.15227/orgsyn.019.0015.

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[2]

[3]

[4]

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Reaction mechanism

Historical references

See also

References

External links