Chemo-selective Synthesis of [indoline-3,4'-isoxazolo[5,4-b]pyridine Fused spirooxindole Derivatives via Brønsted Acid Catalysed Three–Component Tandem Knoevenagel/Michael Addition Reaction

With their exceptional three-dimensional structural topographies, spirooxindoles are known best for privileged chemotypes for diverse biological applications. We report herin a highly convergent and efficient protocol, for the facile chemoselective synthesis of a library of [indoline-3,4′-isoxazolo[5,4-b]pyridine fused spirooxindole derivatives, has been achieved by a Brønsted acid catalyzed three component tandem Knoevenagel/Michael addition. Interestingly, the method not only offers the benefits of operational simplicity, but also chemoselective and atom economic with excellent yields of the targeted molecule. The reaction mechanism and substrate scope of this novel reaction has been thoroughly out lined.