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 °C) and azine derivatives at lower temperature (20 °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.