NaIO 4 ‐Mediated Tandem Oxidative Annulation of Aryl Isocyanides With 2‐Alkynylanilines: Access to Indolo[2,3‐ b ]quinolines

A NaIO 4 ‐mediated oxidative tandem annulation of aryl isocyanides with 2‐alkynylanilines has been developed for the efficient construction of the indolo[2,3‐ b ]quinoline scaffold. Under metal‐free conditions in an EtOH/H 2 O solvent system at room temperature, a series of desired products were obtained in moderate to good yields, with the highest yield reaching 92%, and the reaction exhibited good functional‐group tolerance. Gram‐scale synthesis also proceeded smoothly to afford the product in 86% yield without the need for column chromatographic purification. Preliminary biological evaluation revealed that representative compound 3o showed an inhibitory effect on HCT116 cell proliferation. The transformation is proposed to proceed through a carbodiimide‐related pathway.