AlCl₃‑Promoted Formal [2 + 3]-Cycloaddition of 1,1-Cyclopropane Diesters with <i>N</i>‑Benzylic Sulfonamides To Construct Highly Stereoselective Indane Derivatives

An unprecedented AlCl3-promoted formal [2 + 3]-cycloaddition of 1,1-cyclopropanes with readily available N-benzylic sulfonamides has been developed. Experimental evidence supports an unusual mechanism wherein the donor–acceptor cyclopropane serves as a source of 2-styrylmalonate rather than the “classical” 1,3-dipole. A broad range of 1,1-cyclo­propane­diesters undergo a carbocation-initiated cyclization reaction with N-benzylic sulfonamides to afford highly functionalized Indane derivatives in a fast and high-yielding procedure.