Lossen Rearrangement
Lossen rearrangement is the conversion of a hydroxamate ester to an isocyanate. Lossen rearrangement occus when O-acyl, sulfonyl, or phosphoryl (LG) derivatives of hydroxamic acid are heated with bases. The hydroxamic acids shows tautomerism, the keto form is termed hydroxamic form while the enol form is called hydroxamic acid. Lossen rearrangement differ from Hofmann rearrangement because here in this rearrangement leaving group is carboxalate anion.
