Microwave-assisted Expeditious and Efficient Synthesis of Cyclopentene Ring-fused Tetrahydroquinoline Derivatives Using Three-component Povarov Reaction.

We report here an efficient and expeditious microwave-assisted synthesis of cyclopentadiene ring-fused tetrahydroquinolines using the three-component Povarov reaction catalyzed by indium (III) chloride. This method has an advantage of shorter reaction time (10 - 15 min) with high and reproducible yields (up to 90%) and is suitable for parallel library synthesis. The optimization process is reported and the results from the microwave route are compared with those of the conventional synthetic route. In almost all cases, the microwave acceleration consistently provided improved yields favoring the cis-diastereomer.