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.