Quanyu Ma, Qi Sun, Ningning Li, Jiajing Tan, Jiaxi Xu
The Sc(OTf) 3 -catalyzed (3 + 3) annulation of quinoxaline-2(1 H )-thiones and donor–acceptor cyclopropanes was achieved in the presence of DBU under air to give functionalized 2,3-dihydro-4 H -thiopyrano[2,3- b ]quinoxaline derivatives in moderate to high yields. The annulation includes tandem nucleophilic ring opening, nucleophilic addition, and radical oxidative aromatization. It provides not only a new (3 + 3) annulation strategy but also a new synthetic method for fused tricyclic quinoxaline derivatives.