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Hydroalkylation of alkenes with 1,3-diketones via gold(III) or silver(I) catalysis: divergent mechanistic pathways revealed by a DFT-based investigation

Citation

Jalali, M and Hyland, CJT and Bissember, AC and Yates, BF and Ariafard, A, Hydroalkylation of alkenes with 1,3-diketones via gold(III) or silver(I) catalysis: divergent mechanistic pathways revealed by a DFT-based investigation, ACS Catalysis, 11, (9) pp. 5795-5807. ISSN 2155-5435 (2021) [Refereed Article]

Copyright Statement

© 2021 American Chemical Society

DOI: doi:10.1021/acscatal.0c05260

Abstract

Density functional theory calculations were used to investigate the mechanisms of established hydroalkylation reactions of styrenes with 1,3-diketones that are promoted by either AuCl3/AgOTf or AgOTf catalyst systems. In the former case, our studies led us to propose an original mechanism that is initiated by the generation of highly electrophilic Au(OTf)3, which then coordinates the enol tautomer of the 1,3-diketone substrate. The ensuing highly Brønsted acidic π-complex serves to protonate the styrene to generate a relatively low-energy benzylic carbocation. Notably, this suggests that this benzylic carbocation represents the true catalytic species in the reaction, and thus, the role of the gold complex is solely to generate this active catalyst. AuCl3 alone does not serve as a good initiator for this process because it is not electrophilic enough to generate the relatively low-energy benzylic carbocation. Our investigation of the hydroalkylation facilitated by the slightly electron-deficient AgOTf catalyst revealed that an alternative mechanism predominates. Specifically, it is more likely that the reaction proceeds via a demetallation process directly mediated by the silver catalyst. We found a clear trend indicating that the electron deficiency of the metal center dictates which of these two mechanistic scenarios occurs. This article discusses these two mechanistic pathways in detail, providing key information for the experimental development of hydroalkylation processes.

Item Details

Item Type:Refereed Article
Keywords:density functional theory (DFT), gold(III) catalysis, silver(I) catalysis, hidden carbocation catalysis, hidden Brønsted acid catalysis, reaction mechanism
Research Division:Chemical Sciences
Research Group:Organic chemistry
Research Field:Organic chemical synthesis
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the chemical sciences
UTAS Author:Jalali, M (Ms Mona Jalali)
UTAS Author:Bissember, AC (Associate Professor Alex Bissember)
UTAS Author:Yates, BF (Professor Brian Yates)
UTAS Author:Ariafard, A (Associate Professor Alireza Ariafard)
ID Code:144285
Year Published:2021
Funding Support:Australian Research Council (DP180100904)
Web of Science® Times Cited:1
Deposited By:Chemistry
Deposited On:2021-05-07
Last Modified:2021-06-02
Downloads:0

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