Chemodivergent Ring Annulation of ortho -Bromophenyl Sulfones: Synthesis of π-Expanded Carbazoles and Acridines via Five- and Six-Membered Cyclic Sulfones

A chemodivergent synthetic strategy for the ring-size-selective cyclization of ortho-bromophenyl naphthyl sulfones has been developed. By switching between palladium catalysis and photoredox catalysis, five-membered thiophene S,S-dioxides and six-membered thioxanthene S,S-dioxides were selectively obtained from a common precursor. Subsequent desulfonylative amination with arylamines enabled efficient access to a variety of N-doped polycyclic aromatic hydrocarbons, including dibenzocarbazoles and benzoacridine derivatives. The reactivity of the six-membered sulfones toward amination exhibited distinct patterns, which were rationalized by mechanistic studies and density functional theory calculations based on aromatic resonance energies. Optical investigations of the resulting cyclic amines revealed structure-dependent absorption and emission properties.