Highly Diastereoselective Synthesis of Trifluoromethylated Spirocyclopropanes from 2-(2′-Ketoalkyl)-1,3-Indandiones and CF3-Imidoyl Sulfoxonium Ylides

A metal-free and highly diastereoselective strategy for the synthesis of trifluoromethylated spirocyclopropanes has been developed using CF3-imidoyl sulfoxonium ylides (TFISYs) and 2-(2′-ketoalkyl)–1,3-indandiones. The transformation proceeds through a base-mediated cascade process to furnish densely functionalized trifluoromethylated spirocyclopropanes in good to excellent yields with excellent diastereoselectivity. The protocol exhibits a broad substrate scope, gram-scale applicability, and synthetic versatility through post-functionalization, providing efficient access to fluorinated spirocyclic architectures of potential medicinal relevance.