Cleavage of the C= N Bond in Carbodiimides via Release of High Ring Strain: A New Strategy for the Selective Synthesis of 2-Aminoaryl Alkynyl Imines

A novel pattern of the cleavage and reorganization of CN bond in the multicomponent reaction (MCR) of terminal alkynes or haloalkynes, carbodiimides, and benzynes is achieved for the first time to construct efficiently 2-aminoaryl alkynyl imines. The selective formation and ring-opening of the azetine intermediate with the high ring strain is essential for this reaction. Further transformation of 2-aminoaryl alkynyl imines via the Cu-catalyzed cycloisomerization is explored to provide steroselectively the bi-, tri-, and tetracyclic fused pyrrolines.