Synthesis of functionalized chromeno[2,3-b]pyrrole-2,3-dicarboxylate via Zn(OTf)2-catalyzed annulation of 2-amino-4H-chromen-4-one and electron-deficient Acetylenes

A Zn(OTf)₂-mediated annulation of 2-amino-4H-chromen-4-one with diethyl acetylenedicarboxylate (DEAD) was investigated to provide access to functionalized chromeno[2,3-b]pyrrole-2,3-dicarboxylate in excellent yields with good functional group tolerance. Furthermore, this method also synthesized a variety of novel annulated chromeno[2,3-b]pyrroles (3a-n) through a plausible new mechanism.