Copper-catalyzed aerobic oxidative dehydrogenative cyclization to construct polycyclic aromatic hydrocarbons

Abstract

The copper-catalyzed aerobic oxidative dehydrogenative cyclization of benzo[b]thiophene represents an efficient approach for the rapid construction of polycyclic aromatic hydrocarbons (PAHs) containing benzo[b]thiophene groups. However, this remains an underexplored field. Here, we establish a new type of copper-catalyzed aerobic oxidative dehydrogenative cyclization of benzo[b]thiophene that enables the utilization of benzo[b]thiophene functionality to access polycyclic aromatic hydrocarbons. This methodology features mild reaction conditions, high atom economy, and remarkable chemo-selectivity, delivering a diversity of PAHs containing benzo[b]thiophene groups. Mechanistic experiments and DFT calculations demonstrate that the in situ generation of benzothiophenyl radical cation intermediate undergoes the intermolecular cyclization and the capture of H2O to furnish the oxidative cycloaromatization reaction. Labeling experiment disclosed that the carbonyl oxygen atom of the product originates from H2O generated during the reaction.