Catalytic Regioselective Synthesis of Structurally Diverse Indene Derivatives from N-Benzylic Sulfonamides and Disubstituted Alkynes

An unprecedented protocol has been developed for the regioselective synthesis of structurally diverse indene derivatives from readily accessible N-benzylic sulfonamides and disubstituted alkynes through FeCl3-catalyzed cleavage of sp(3) carbon nitrogen bonds to generate benzyl cation intermediates. In the presence of 10 mol % of FeCl3, a broad range of N-benzylic sulfonamides smoothly react with internal alkynes, alkynylcarbonyl compounds, alkynyl chalcogenides, or alkynyl halides to afford various functionalized indene derivatives with extremely high regioselectivity.