Amino‐Ene Click Reaction of Electron‐Deficient π‐Conjugated Molecules with Negative Activation Enthalpies

An amino-ene click reaction is a type of aza-Michael addition reaction that is congruent with click chemistry in terms of its reaction efficiency and rate under mild conditions. The amino-ene click reaction is increasingly recognized as a prominent synthetic tool to form C–N bonds in the context of organic materials chemistry and polymer chemistry. Herein we report an unconventional amino-ene click reaction with negative activation enthalpies, where an electron-deficient π-conjugated molecule such as a naphthalenediimide reacts with an amine faster at lower temperatures. The detailed study of the reaction mechanism reveals that the amino-ene click reaction proceeds via a pre-equilibrium reaction, the key to which is the formation of a stable reaction intermediate due to the solvation and charge delocalization on the π-core. By optimizing the reaction conditions, we demonstrated that the amino-ene click reaction proceeded faster at 273 K than at 347 K, which was easily observed visually.