A cationic gold(l) complex with a semihollow-shaped trialkynylphosphine catalyzed 5-exo-dig and 6-endo-dig cyclizations of various internal alkynic beta-keto esters, showing a marked advantage over a gold(I)-PPh3 complex with respect to the rates of the reactions and the product yields. It is proposed that the gold-bound alkynic substrate in a catalytic pocket must be somewhat folded and that such a steric effect makes the carbon-carbon bond formation entropically more favorable.
Gold(I)-Catalyzed Conia-ene Cyclization of Internal <i>ϵ</i>
-Acetylenic β-Ketoesters under High Pressure.
the gold(I)‐catalyzed Conia‐ene cyclization of ϵ‐acetylenic‐β‐ketoesters bearing an internal alkyne moiety was investigated for the first time. The reaction catalyzed by commercially available PPh3AuNTf2 complex, which is sluggish at ambient pressure owing to steric reasons, proceeds smoothly under high‐pressure conditions (6 kbar). Mechanistic aspects of the reaction proceeding via 5‐exo‐dig and 6‐endo‐dig