Diethyl Azodicarboxylate-Promoted Oxidative [3 + 2] Cycloaddition for the Synthesis of Pyrrolo[2,1-a]isoquinolines.

A novel metal-free protocol for the effective and efficient construction of pyrrolo[2,1-a]isoquinolines via a diethyl azodicarboxylate (DEAD)-promoted oxidative [3 + 2] cycloaddition/aromatization tandem reaction is described. Instead of the reported two-component oxidation systems, DEAD, as the sole oxidant, could smoothly transfer the tertiary amines to azomethine ylides via oxidation-deprotonation tandem process. The reaction proceeded with a broad substrate scope, giving rise to products in moderate to good isolated yields.