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Mechanisms and Origins of Chemoselectivities of Gold(I)‐Catalyzed Nitrogenations of Alkynes with Trimethylsilyl Azide: A Computational Study
Author(s) -
Wen Xiuling,
Deng Jiaojiao,
Sheng Qiang,
Li Juan
Publication year - 2017
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201701061
Subject(s) - chemoselectivity , chemistry , alkyne , nucleophile , trimethylsilyl , medicinal chemistry , catalysis , azide , stereochemistry , organic chemistry
Recently, Jiao and co‐workers reported an unprecedented gold‐catalyzed nitrogenation of alkynes with trimethylsilyl azide through C–C and C≡C bond cleavages. In this reaction, the acidic additive controls the chemoselectivity for the formation of either carbamides or aminotetrazoles from an internal alkyne. In this study, density functional theory calculations were performed to clarify the mechanism and origin of this chemoselectivity. A systematic search shows that the acidities of CH 3 SO 3 H and CF 3 SO 3 H determine which of the two reaction pathways is followed and, thus, the chemoselectivity. CH 3 SO 3 H favors the hydroxylation step and eventually leads to carbamide production. In contrast, CF 3 SO 3 H, which is a stronger acid than CH 3 SO 3 H, favors trimethylsilyl removal and eventually generates aminotetrazoles. This acid‐dependent chemoselectivity also applies to terminal alkynes and is consistent with the corresponding experimental results. Both CH 3 SO 3 H and CF 3 SO 3 H form carbamides preferentially because the hydrogen atom in a terminal alkyne promotes nucleophilic hydration more effectively than the n ‐butyl group in an internal alkyne.