Iodocyclization Route to Indolo- and Pyrroloquinolines

Significance

Based on previous experience in preparing similar scaffolds, a route to indolo- and pyrrolo[1,2-a]quinolines was devised, tested, and extended to multiple substrates. The starting materials, conveniently prepared via Sonogashira coupling, were subjected to iodocyclization and optimized conditions by variation of halide source and solvent were established. The substrate scope was well studied for this efficient high-yielding process. The method seems to be robust for substrates bearing electron-donating and neutral groups, but R^¹ and R^³ containing para-positioned electron-withdrawing groups led to complex and inseparable mixtures of products. Additionally, a 5-OMe indole derivative failed.