Selective Enyne Ring-Closing Metathesis with Main Group Metal Catalysts

Ring-closing metathesis (RCM) represents an ideal and atom-economical way to construct cyclic compounds. The precedented reaction systems for endo-selective enyne RCM mainly rely on precious transition metal carbene complexes or activated substrates. Here we report the utility of group 13 metal halides, such as InBr3 and InI3, as simple and efficient catalysts for endo-selective RCM of nitrogen-tethered 1,6-enynes under mild conditions. Conventionally, these substrates underwent cycloisomerization to generate 6,3-fused bicycles under transition metal catalysis. The reaction mechanism and nature of the catalytic species have been revealed by kinetic experiments and density functional theory calculations.