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 electrondensity of the nitrogen atom was delocalised more over the aromatic rings than the triple bond.