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

Abstract

AbstractAn 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, an unconventional amino‐ene click reaction with negative activation enthalpies, in which an electron‐deficient π‐conjugated molecule, such as a naphthalenediimide, reacts with an amine faster at lower temperatures is reported. 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, it was demonstrated that the amino‐ene click reaction proceeded faster at 273 K than at 347 K, which was easily observed visually.