Catalyst-Free Reaction of Ethynyl-π-Extended Electron Acceptors with Amines

Imide- or amide-based pi-systems, as represented by naphthalenediimides (NDIs), perylenediimides (PDIs), or diketopyrrolopyrroles (DPPs), have been extensively studied owing to their characteristic optical properties, their electronic structures, and so forth. Here, we present syntheses of NDIs, a PDI, and a DPP with ethynyl substituents, and their use as new building blocks for the synthesis of amino-functionalized electron-accepting pi-conjugated systems. The reaction between the ethynyl group of the electron acceptor and an amine proceeds almost quantitatively, without a catalyst, to give a Michael-addition-type product that shows remarkable changes in its optical properties, redox properties, and dipole moment. The progress of the reaction can be visually monitored in various media. On the basis of a kinetic analysis of the amine-addition reaction, various amino-functionalized asymmetric and symmetric n-systems were obtained in a designed manner.