Rhodium(III)-Catalyzed Sequential Cyclization of N-Boc Hydrazones with Propargylic Monofluoroalkynes via C–H Activation/C–F Cleavage for the Synthesis of Spiro[cyclobutane-1,9′-indeno[1,2-a]indenes]

An effective rhodium(III) catalysis for the construction of valuable tetracyclic compounds is described herein. This domino process involving the C–H activation/[3 + 2] annulation/intramolecular Friedel–Crafts reaction sequences of simple and readily available N-Boc hydrazones and propargylic monofluoroalkynes afforded fused tetracyclic spiro[cyclobutane-1,9′-indeno[1,2-a]indenes] in moderate to good yields, featuring three C–C bond formation. Moreover, control experiments indicated that the C–H activation might be involved in the rate-determining step.