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.

中文翻译：

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通过金（I）催化氨化/亲核取代反应形成苯舒坦的计算研究

通过密度泛函理论 (DFT) 计算研究了 (2-炔基) 苯基磺酰基氮杂环丁烷在作为质子亲核试剂的甲醇存在下，Au(I) 催化反应形成苯磺胺衍生物。我们的研究强调，金（I）催化炔烃上氮的亲核加成优于氮杂环丁烷通过甲醇直接开环，证实了基于铵的机制。此外，通过实验观察到的反向区域选择性，其中非末端炔烃有利于 6 - endo -dig-benzosultams的形成，而末端炔烃有利于 5- exo-dig 产品也通过两种不同的场景进行探索。第一个包含单个 Au(I) 物种对炔烃的经典活化，而第二个则解决 σ,π-二金乙炔配合物的形成。尽管只有单金 (I) 配合物才能产生最终产品，但计算表明这两种途径都具有竞争力，这与实验观察结果非常一致。还讨论了存在过量质子亲核试剂对原脱金属步骤和最终缩醛胺形成的重要性的进一步细节。