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

The synthesis of trifluoromethyl (CF 3 )- and pentafluorosulfanyl (SF 5 )-substituted cyclopropane-fused γ-lactones was carried out through Rh 2 (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 CF 3 - and SF 5 -substituted cyclopropanes. These novel SF 5 -substituted analogues join the very short list of available pentafluorosulfanyl intermediates.