Regioselective [3+3] Cyclization of 2-Indolymethanols with Vinylcyclopropanes via Metal Catalysis

The first [3+3] cyclization of 2-indolylmethanols with vinylcyclopropanes has been established under iridium catalysis. The reaction regioselectively constructs tetrahydrocarbazole frameworks bearing two vicinal all-carbon quaternary stereocenters in high yields (up to 99%, up to 20:1 rr). This reaction not only is the first example of a metal-catalyzed [3+3] cyclization of 2-indolylmethanols but also is the first one-step [3+3] cyclization of vinylcyclopropanes. More importantly, this reaction shows reversed regioselectivity compared to other 2-indolylmethanol-involved transformations, which will advance the chemistry of 2-indolylmethanols.