Synthesis of Substituted Carbazoles, Indoles, and Dibenzofurans by Vinylic to Aryl Palladium Migration

Substituted carbazoles, indoles, and dibenzofurans are readily prepared in moderate to excellent yields by the palladium-catalyzed cross-coupling of alkynes and appropriately substituted aryl iodides. This process proceeds by carbopalladation of the alkyne, heteroatom-directed vinylic to aryl palladium migration, and ring closure via intramolecular arylation or a Mizoroki-Heck reaction. Results from the deuterium labeling experiments are consistent with the proposed mechanism.