Synthesis of 2-Hydroxycarbazoles via Rh(III)-Catalyzed Cascade Cyclization of Indolyl Nitrones with Alkylidenecyclopropanes

The synthesis of functionalized carbazoles is an important tool in the discovery of bioactive molecules. Herein, we present a method for synthesizing 2-hydroxycarbazoles from indolyl nitrones and alkylidenecyclopropanes under Rh(III) catalysis. A notable reaction pathway involves [3 + 2] cycloaddition between indolyl nitrones and diene intermediates, followed by aromatization and reductive N-O bond cleavage in a cascade manner. Moreover, a series of post-transformations highlights the utility of the proposed method.