Catalytic Transformations of Alkynes into either α‐Alkoxy or α‐Aryl Enolates: Mannich Reactions by Cooperative Catalysis and Evidence for Nucleophile‐Directed Chemoselectivity

Abstract The catalytic formation of gold enolates from alkynes, nitrones, and nucleophiles is described, and their Mannich reactions result in nucleophile‐directed chemoselectivity through cooperative catalysis. For 1‐alkyn‐4‐ols and 2‐ethynylphenols, their gold‐catalyzed nitrone oxidations afforded N‐containing dihydrofuran‐3(2 H )‐ones with syn selectivity. The mechanism involves the Mannich reactions of gold enolates with imines through an O‐H‐N hydrogen‐bonding motif. For aryloxyethynes, their gold enolates react selectively with nitrones to deliver 3‐alkylidenebenzofuran‐2‐ones, as controlled by a C‐H‐O hydrogen‐bonding motif.