Diastereoselective ABB' Three-Component Synthesis of Highly Functionalized Spirooxindoles Bearing Five Consecutive Asymmetric Carbons.

The synthesis of spirooxindoles bearing tetrahydro-4H-cyclopenta[b]furan framework was established starting from isatin-derived aldehydes and two equivalents of 1,3-dicarbonyl compounds involving a piperidine-catalyzed ABB' three-component domino process. This reaction was highly diastereoselective affording a single diastereomer of spirooxindoles with five consecutive asymmetric carbons including a spiro and tetrasubstituted carbon centers. In addition, this waste-free (-2H2O) reaction showed high atom- and step economy by creating four new bonds including three C-C and one C-O bonds, and two rings (one carbo- and one heterocycle) in a single operation. The mechanism of this three-component domino process involved sequential Knoevenagel condensation-Michael addition-intramolecular oxa-Michael addition-intramolecular aldol reactions.