Copper-Catalyzed Hydrogen/Iodine Exchange in Terminal and 1-Iodoalkynes

Detailed kinetic profiles of the copper-catalyzed exchange between the acetylenic proton and iodide of terminal and 1-iodophenylacetylenes are reported. The electronic nature of the alkynes does not influence the equilibrium of the exchange (Keq = 1), only the rate of equilibration. Notably, the profiles are the same for electron-rich, methyl-substituted phenylacetylenes but are divergent for electron-deficient, trifluoromethyl-substituted variants. The heretofore unreported exchange process yields practical considerations regarding reactions involving iodo and terminal alkynes.