Synthesis of CF3-Containing 3,3′-Cyclopropyl Spirooxindoles by Sequential [3+2] Cycloaddition/Ring Contraction of Ylideneoxindoles with 2,2,2-Trifluorodiazoethane

A [3 + 2] cycloaddition/ring contraction sequence of ylideneoxindoles with in situ-generated 2,2,2-trifluorodiazoethane without the use of any transition-metal catalyst has been developed. The reaction provides efficient access to biologically important and synthetically useful CF3-containing 3,3'-cyclopropyl spirooxindoles in high yield (74-99%) with high diastereoselectivity (>95:5 d.r.).