Transition-Metal-Free Synthesis of Carbazoles and Indoles by an SNAr-Based "aromatic Metamorphosis" of Thiaarenes

Article abstract of DOI:10.1002/anie.201503671

Dibenzothiophene dioxides, which are readily prepared through oxidation of the parent dibenzothiophenes, undergo nucleophilic aromatic substitution with anilines intermolecularly and then intramolecularly to yield the corresponding carbazoles in a single operation. The "aromatic metamorphosis" of dibenzothiophenes into carbazoles does not require any heavy metals. This strategy is also applicable to the synthesis of indoles. Since electron-deficient thiaarene dioxides exhibit interesting reactivity, which is not observed for that the corresponding electron-rich azaarenes, a combination of a thiaarene-dioxide-specific reaction with the S_NAr-based aromatic metamorphosis allows transition-metal-free construction of difficult-to-prepare carbazoles.