Synthesis of Cyclopropane Spirooxindoles by means of a Vinylogous Organocatalytic Cascade

The stereoselective construction of spirooxindolic cyclopropane derivatives is achieved by means of a vinylogous cascade reaction that successfully integrates a vinylogous iminium ion/dienamine tandem sequence. The chemistry capitalizes upon a rare example of asymmetric 1,6-addition to 2,4-dienals, which proceeds with exclusive δ-site selectivity.