Iodine-Mediated Site-Selective C-H Chalcogenation of Carbazoles

We report a metal-free and iodine-mediated approach for the regioselective C-H chalcogenation of NH-unprotected carbazoles. Both mono- and dithioarylated carbazoles were synthesized using diaryl disulfides or aryl thiols without the need for transition-metal catalysts or N-protection. The reaction selectivity was tuned by choice of solvent and temperature, allowing access to C3- or C3,C6-thioarylated products with good efficiency. Furthermore, the method was extended to the C-H selenylation of carbazoles using diaryl diselenides, delivering mono- and diselenylated derivatives in moderate to good yields. Mechanistic studies indicate a radical pathway involving thiyl or selenyl radicals. This operationally simple, scalable protocol provides a versatile platform for directly functionalizing NH-free carbazoles with chalcogen motifs, offering new opportunities in synthesizing heteroatom-rich organic materials and bioactive scaffolds.