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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 AriafardDensity 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
OrganometallicsVolume
38Pagination
489-497ISSN
0276-7333Department/School
School of Natural SciencesPublisher
Amer Chemical SocPlace of publication
1155 16Th St, Nw, Washington, USA, Dc, 20036Rights statement
© 2018 American Chemical SocietyRepository Status
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