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Curtius Rearrangement


The Curtius rearrangement is a very general reaction and can be applied to carboxylic acids containing a wide range of functional groups. It is also possible to include a curtius rearrangement under photochemical conditions, but this pathway gives rise to several side-products in addition to the desired isocyanate. Curtius rearrangement with various acid chlorides including phenoxy acetyl chloride.

Curtius Rearrangement

Curtius rearrangement precursors can also be prepared from acyl chlorides using tributylstannyl azide. An alkylamino fullerene derivative was prepared from acyl chloride.


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The curtius reaction involves the Curtius rearrangement and hence the Curtius rearrangement should be understood first. The acyl azide (R-CON3) decomposes into isocyanate by gentle heat in inert solvents like benzene, chloroform etc.

RCON3 $\overset{\Delta }{\rightarrow}$ R-N=C=O + N2

The driving force for Curtius rearrangement is the electron deficient nitrogen formed on elimination of N2 molecule on heating.

Curtius Rearrangement Mechanism

The curtius reaction involves the conversion of acids to amines, urethanes and substituted urea via curtius rearrangement.

Curtius Reaction

Thermal or photochemical rearrangement of acyl azides into amines via isocyanate intermediates. While the thermal rearrangement is a concerted process, the photochemical rearrangement goes through a nitrene intermediate.


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The curtius rearrangement provides a way to replace a carboxyl group with amine functionality, a transformation of pronounced synthetic value. Streamlined preparation of the starting acyl azides, alternative methods that avoid isolation of these potentially unstable acyl azides altogether and improved ways to intercept the isocyanate products, including metal-catalyzed reactions, have added to the preparative utility of the curtius rearrangement.

Curtius Reaction Application

Curtius rearrangement including many excellent examples while describing some classic examples, will emphazise recent application of the reaction, including its application in synthetically challenging, highly functionalized molecular framework.