The reaction of acyl cyanides with "Huisgen zwitterion": an interesting rearrangement involving ester group migration between oxygen and nitrogen atoms.

A novel rearrangement involving ester group migration was found in the reaction of acyl cyanides and Huisgen zwitterions, affording hydrazone derivatives at higher temperature (90 degrees C) and azine derivatives at lower temperature (20 degrees C), respectively. Interestingly, the reaction temperature is identified as a critical factor to control the final products. Presumably, the rearrangement involving ester group migration between oxygen and nitrogen atoms leads to the formation of different products.