Zinc Triflate as Lewis Acid in Nucleophilic Addition to Cyclic N-Acyliminium Ions

Zinc triflate-mediated nucleophilic addition of allytrimethylsilane, silyl enol ethers and terminal acetylenes to cyclic N-acyliminium ions at room temperature in CH 2 Cl 2 is described. The corresponding α-substituted heterocycles were obtained in moderate to good yields. The versatility of this reagent was demonstrated in the one-pot generation of the N-acyliminium ion and the zinc alkynylide species, followed by their coupling reaction to afford propargylic adducts in moderate yields.