Computational Study of Benzosultam Formation through Gold(I)‐Catalyzed Ammoniumation/Nucleophilic Substitution Reaction

Abstract

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

Computational insight into gold(i)-catalyzed intramolecular regioselectivity of tryptamine-ynamide cycloisomerizations

“…[1][2][3][4][5][6][7][8] The reaction pathways of these cycloisomerizations are determined by a variety of parameters, such as solvents, [9][10][11][12] catalysts, [13][14][15] ligands, [16][17][18][19][20] and substitutions. [21][22][23][24][25][26] These pathway-switchable reactions enable chemists to synthesize molecules with different scaffolds from the same or similar reactants only by tuning these parameters of the reactions. They afford a useful synthetic toolbox for generating small molecules through divergent pathways, which can improve the efficiency of organic reactions.…”