AlCl3-promoted formal [2 + 3]-cycloaddition of 1,1-cyclopropane diesters with N-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.