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Mechanistic elucidation of gold(I)-catalyzed oxidation of a propargylic alcohol by a N-oxide in the presence of an imine using DFT calculations

journal contribution
posted on 2023-05-20, 06:19 authored by Zarkoob, F, Alireza AriafardAlireza Ariafard
Density functional theory (DFT) calculations were utilized to investigate the mechanism of the oxidation of an indolyl propargylic alcohol by a N-oxide in the presence of an imine and a gold(I) catalyst. The catalytic reaction is proposed to start from regioselective oxidation of the gold(I)-activated alkyne dictated by a hydrogen bond interaction between the OH group of the propargylic alcohol and the N-oxide. This oxidation was expected to give an α-carbonyl gold carbene complex. In contrast to this expectation, our calculations showed that the corresponding carbene is not a local minimum and the complex undergoes a very fast 1,2 aryl shift to form an alkene complex. Subsequently, an imine is added to the ensuing alkene complex to give an iminium cation from which a cycloaddition process occurs and an indolium is formed. Finally, an N-oxide deprotonates the indolium complex and affords an intermediate which is significantly reactive toward water elimination. Our calculations indicate that the 1,2-aryl shift in α-carbonyl gold carbene complexes is decelerated if the aryl is substituted by an electron-withdrawing group. At the end, we investigated the stability of different gold carbene complexes and found that the identity of the carbene is the determinant of how these carbenes are trapped.

Funding

Australian Research Council

University of Wollongong

History

Publication title

Organometallics

Volume

38

Pagination

489-497

ISSN

0276-7333

Department/School

School of Natural Sciences

Publisher

Amer Chemical Soc

Place of publication

1155 16Th St, Nw, Washington, USA, Dc, 20036

Rights statement

© 2018 American Chemical Society

Repository Status

  • Restricted

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Expanding knowledge in the chemical sciences

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