Issue 6, 2017

Thiolate–palladium(iv) or sulfonium–palladate(0)? A theoretical study on the mechanism of palladium-catalyzed C–S bond formation reactions

Abstract

The density functional theory (DFT) method M06-L was used to study the general mechanism of palladium-catalyzed C–S bond formation reactions. Our theoretical calculations revealed that this type of reaction starts with a palladium-assisted metalation–deprotonation step. Oxidative addition of the sulfur source affords a thiolate–palladium(IV) intermediate, and subsequent reductive elimination generates the new C–S bond. A final protonation regenerates the active palladium(II) catalyst and releases the product. Our proposed mechanism could be applied to a series of palladium-catalyzed C–S bond formation reactions used for the construction of dibenzothiophene derivatives. The rate-limiting step of the catalytic cycle is oxidative addition to yield the thiolate–palladium(IV) intermediate. In contrast, formation of a sulfonium intermediate is unfavourable. In addition, the effect of substituents on the rate-determining step was studied with Hammett plots. Our calculations showed that incorporation of electron-withdrawing groups at the 4-position and electron-donating groups at the 15 and 16-positions would promote intramolecular oxidative addition of thioethers to palladium.

Graphical abstract: Thiolate–palladium(iv) or sulfonium–palladate(0)? A theoretical study on the mechanism of palladium-catalyzed C–S bond formation reactions

Supplementary files

Article information

Article type
Research Article
Submitted
22 dec 2016
Accepted
13 jan 2017
First published
17 jan 2017

Org. Chem. Front., 2017,4, 943-950

Thiolate–palladium(IV) or sulfonium–palladate(0)? A theoretical study on the mechanism of palladium-catalyzed C–S bond formation reactions

D. Xu, X. Qi, M. Duan, Z. Yu, L. Zhu, C. Shan, X. Yue, R. Bai and Y. Lan, Org. Chem. Front., 2017, 4, 943 DOI: 10.1039/C6QO00841K

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