The Lossen rearrangement is the conversion of an acyl hydroxamate to an isocyanate and carboxylic acid side product. 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 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.
See also Curtius rearrangement Hofmann rearrangement Schmidt reaction Beckmann rearrangement Gabapentin Glucosinolate § Enzymatic activation
Historical references Lossen, W. (1872).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
External links "Mechanism in Motion: Lossen rearrangement". 7 October 2010 – via YouTube.