Computational Study of Benzosultam formation via Gold(I)‐Catalyzed Ammoniumation / Nucleophilic Substitution Reaction

The Au(I)-catalyzed reactions of (2-alkynyl)phenylsulfonyl azetidines bearing terminal and non-terminal alkynes in the presence methanol as protic nucleophile to form benzosultams derivatives were studied by density functional theory (DFT) calculations. Our study highlights that gold(I) catalyzed nucleophilic addition nitrogen on alkyne is favored over direct ring opening azetidine methanol, confirming ammonium-based mechanism. In addition, reverse regioselectivity observed experimentally where favors formation 6-endo-dig-benzosultams while favor 5-exo-dig products also explored through two different scenarios. first one embraces classical activation a single Au(I) species second tackles σ,π-digold acetylide complex. Calculations identify both pathways competitive although only mono complexes can lead final products, good agreement with experimental observation. Further details importance an excess protodemetallation step aminal discussed.