Finally, other alkynylation reagents were investigated (Scheme 1 -c and d), giving to the Ph-acetylene salt 1r in 60% yield. For the 1-hexyne derivative the one-pot procedure was not successful, so that the oxidized intermediate was isolated and used for the alkynylation. Here, only the vinyl species 1s could be isolated due to the addition of TfOH to the alkyne. This behavior has previously been described for other unsubstituted as well as stabilized iodonium salts. For salts containing a free NH-function in the N-heterocycle, the corresponding cyclic ENHIs were synthesized through addition of aqueous NaHCO 3 -solution to the reaction mixture after the alkynylation step (Scheme 2).