Rare-Earth-Metal-Catalyzed Addition of Terminal Monoalkynes and Dialkynes with Aryl-Substituted Symmetrical or Unsymmetrical Carbodiimides

A high-efficiency and atom-economic route for the synthesis of N-aryl-substituted propiolamidines was established through the addition of terminal alkynes with aryl-substituted symmetrical or unsymmetrical carbodiimides catalyzed by mixed TpMe2/Cp rare-earth-metal alkyl complexes (TpMe2)­CpLnCH2Ph­(THF) (1Ln). Moreover, the gadolinium alkyl complex 1Gd can also serve as a catalyst for the double addition of dialkynes with carbodiimides. Mechanism studies indicated that the variable coordination modes (κ3 or κ2) of the TpMe2 ligand on the rare-earth-metal species may play an important role in the catalytic cycles.