Synthesis of orthogonal push–pull chromophores via click reaction of arylynamines

Abstract

Herein, we report a catalyst-free ‘click’ reaction: metal-free [2 + 2] cycloaddition–retro-electrocyclisation (CA–RE) of arylynamines with the sluggish acceptor tetracyanoquinodimethane (TCNQ) to provide orthogonal electron-push–pull light-harvesting small molecules: N-heterocyclic dicyanoquinodimethane-substituted methylene malononitriles. Ynamines are reactive alkynes and tend to induce over-reactions with the CA–RE adducts. The reactivity of arylynamines was balanced properly by ensuring the electron-density of the nitrogen atom was delocalised more over the aromatic rings than the triple bond.