Acid-Promoted Intramolecular Decarbonylative Coupling Reactions of Unstrained Ketones: A Modular Approach to Synthesis of Acridines and Diaryl Ketones.

Herein, we reported Lewis acid- or Brønsted acid-promoted intramolecular C(sp2)-C(sp2) bond cleavage and a novel C(sp2)-C(sp2) bond-forming cascade reaction to synthesize the acridine motif. The metal-free oxidation of the alkyne motif generated the in situ ketone group extracted via a decarbonylation reaction. The mechanistic studies revealed that the electrophilic N-iodo species triggered key decarbonylation reactions via consecutive dearomatization/aromatization reactions. In addition, we exploited this acid-promoted C-C bond activation system with internal alkynes to synthesize bis(heteroaryl) ketones.