Bifunctional Iron Catalyst for Endoselective Cycloisomerization of Nucleophile-Functionalized Terminal Alkynes

The catalytic cycloisomerization of nucleophile-functionalized alkynes is a useful method for the synthesis of heterocyclic compounds with 100% atom economy. Group 8 catalysts give high endoselectivity in these transformations due to their ability to invoke metal-vinylidene intermediates. While many ruthenium and osmium catalysts have been reported, the iron counterpart is underdeveloped. Herein we report a well-defined molecular iron catalyst that can convert a variety of nucleophile-functionalized alkynes into the corresponding heterocycles in an endo-selective manner at ambient temperature and the mechanistic insight of the endoselectivity.