Highly Regioselective and Diastereoselective, One-Pot, Four-Component Synthesis of Novel Spiroindenoquinoxalineindolizidine Derivatives

A one-pot, four-component procedure for the synthesis of novel spiroindenoquinoxalineindolizidines with high regioselectivity and diastereoselectivity from the 1,3-dipolar cycloaddition of azomethine ylides, generated from indenoquinoxalines and pipecolinic acid, and chalcones is described. The reaction occurs under reflux of ethanol as a green solvent and in the absence of any catalyst. The cycloadducts are obtained purely without future purification. The regiochemistry and stereochemistry of resultant cycloadducts have been determined by several 2D-NMR spectroscopic techniques and X-ray single crystal diffraction.