A convenient synthesis of new chromophoric tetracyanobutadiene-scaffolded peptides via a dipolar [2+2] cycloaddition–cycloreversion reaction

Herein, we report a novel approach for the synthesis of π-conjugated peptide-based donor–acceptor (D-π-A) chromophores, by reacting electron-rich alkynes with tetracyanoethylene. The desired tetracyanobutadiene-scaffolded peptides were obtained in good yields with various optical properties, λmax: 321–492 nm, ε: 21,000–65,000 mol−1 dm3 cm−1 depending on the substitution pattern of the cyanobutadiene scaffold.