A copper sulfate pentahydrate-catalyzed intramolecular Friedel–Crafts reaction using an oxocarbenium species derived from a furan ring as the alkylating agent was developed for the first time. By using this protocol, spirofurooxindoles 9 with multi-reactive sites were synthesized simply and concisely. In addition, selective hydrogenation of the endo-cyclic double bond and full hydrogenation of the
Metal-Free Rearrangement of Spirofurooxindoles into Spiropentenoneoxindoles and Indoles: Implications for the Mechanism and Stereochemistry of the Piancatelli Rearrangement
Spirofurooxindoles derived from α-furylcarbinols were rearranged into spirocyclopentenoneoxindoles exclusively or as a mixture of spirocyclopentenoneoxindoles and indoles under different reaction conditions. Along with our previous studies, the stepwise C-Piancatelli rearrangement has been presented for the first time.