Y. Liang, P.-Z. Liu, C.-C. Wu, and Q. Zhang, “Lewis Acid Catalyzed C-N Bond Formation: Synthesis of Quinoxalines via CuX (X = Cl, Br, I) Catalyzed Cyclotrimerization of Alkynes with o-Phenylendiamines”, ajc, vol. 27, no. 11, pp. 3921–3924, Jul. 2015.