The Aza Curtius Rearrangement
On interaction of N-(trifluoromethylsulfonyl)carboximidoyl chlorides (analogs of acyl chlorides in which the carbonyl oxygen atom is substituted by the more strongly electron-withdrawing =NSO2CF3 group) with sodium azide in glyme or acetonitrile at −5 to +10 °C, dinitrogen is eliminated quantitatively and carbodiimides RN=C=NSO2CF3 are formed in high yield. In other words, an aza Curtius rearrangement occurs. The carbodiimides react with water, alcohols, and secondary amines to give corresponding ureas, isoureas, and guanidine derivatives. Imidoyl chlorides with substituents other than SO2RF do not enter into the aza Curtius reaction.