Rhodium-Catalyzed Intramolecular Cyclopropanation of Trifluoromethyl- and Pentafluorosulfanyl-Substituted Allylic Cyanodiazoacetates.

The synthesis of trifluoromethyl (CF3)- and pentafluorosulfanyl (SF5)-substituted cyclopropane-fused γ-lactones was carried out through Rh2(esp)2-catalyzed intramolecular cyclopropanation in up to 99% yields. Twelve examples of this interesting scaffold are reported, as well as postfunctionalizations that provide access to highly functionalized CF3- and SF5-substituted cyclopropanes. These novel SF5-substituted analogues join the very short list of available pentafluorosulfanyl intermediates.