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. Go with the flow: An organocatalytic vinylogous cascade reaction, which yields valuable spirooxindolic cyclopropane derivatives, is presented. This operationally simple chemistry is performed at room temperature and leads to the one-step formation of highly enantioenriched complex frameworks. The cascade follows a 1,6-addition/intramolecular SN2-alkylation sequence driven by vinylogous iminium ion/dienamine activation. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.