Efficient Activation of 2‐Iminomethylpyridine/Cobalt‐Based Alkyne [2+2+2] Cycloaddition Catalyst by Addition of a Silver Salt

The addition of silver triflate (AgOTf) or silver hexafluoroantimonate (AgSbF 6 ) significantly increased the activity of the 2‐(arylimino)methylpyridine/cobalt(II) chloride hexahydrate (CoCl 2 ⋅6 H 2 O)/zinc catalyst in alkyne cyclotrimerizations thereby accelerating the reaction and enabling the use of unactivated, simple internal alkynes as the monoyne substrate: The rate of reaction was found to be highly dependent on the nature of the counter anion (X − ) and the ligand (L) in the postulated cationic cobalt(I) complex [LCo(I)] + X − .