Tandem Synthesis of Pyrrolo[2,3‑b]quinolones via Cadogen-Type Reaction

A tandem [3 + 2] cycloaddition/reductive cyclization of nitrochalcones with activated methylene isocyanides for the efficient synthesis of pyrrolo­[2,3-b]­quinolones is reported. In this reaction, the in situ generated dihydropyrroline acts as the internal reductant to convert the nitro into an electrophilic nitroso group, which undergoes subsequent C–N bond formation. Transition-metal-free, simple experimental procedure and ready accessibility of starting materials characterize the present transformation.