A Streamlined Approach to Indoles, Pyrroles, and Benzimidazoles via Redox-Neutral Aromatization and CO Reduction...

The synthesis of nitrogen heteroarenes has a rich history, including many illustrious name reactions. These reactions often involve complex oxidative processes or the need for transition metal catalysts, and the synthesis of different N-heteroarenes typically requires a case-by-case approach. Here, we have discovered the conversion of vicinal alkyl and nitro groups on arenes or alkenes into an array of N-heteroarenes, including indoles and pyrroles. Moreover, our approach also facilitates the synthesis of benzimidazoles from ortho NH-alkyl nitroarenes. This versatile method leverages a redox-neutral aromatization and CO reduction sequence, uniquely utilizing Cs₂CO₃, and is remarkable for its omission of any transition metals. Our strategy is particularly noteworthy for its exceptional atom, step, and redox efficiency, offering significant advantages for the synthesis of alkaloids that are important in pharmaceutical applications. Extensive experimental and computational studies have allowed us to understand the preferred mechanistic pathways for these heteroarene formations.