Regioselective Transition Metal-Free Catalytic Ring Opening of 2H-Azirines by Phenols and Naphthols; One-Pot Access to Benzo- and Naphthofurans

Benzofuran and naphthofuran derivatives are synthesized from readily available phenols and naphthols. Regioselective ring openings of 2H-azirine followed by in situ aromatization using a catalytic amount of Bronsted acid have established the novelty of the methodology. The involvement of a series of 2H-azirines with a variety of phenols, 1-naphthols, and 2-naphthols showed the generality of the protocol. In-depth density functional theory calculations revealed the reaction mechanism with the energies of the intermediates and transition states of a model reaction. An alternate pathway of the mechanism has also been proposed with computer modeling.

Automated summary

Benzofuran and naphthofuran derivatives were synthesized from readily available phenols and naphthols through regioselective ring openings of 2H-azirines followed by in situ aromatization using a catalytic amount of Bronsted acid. The generality of the protocol was demonstrated by the involvement of a series of 2H-azirines with a variety of phenols, 1-naphthols, and 2-naphthols.