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Computational Insights into Intramolecular Cross-Coupling of Quaternary Borate Salts

preprint
submitted on 16.02.2021, 08:42 and posted on 17.02.2021, 05:04 by Florian Matz, Arif Music, Dorian Didier, Thomas C. Jagau
Cross-coupling reactions for C-C bond formation represent a cornerstone of organic synthesis. In most cases, they make use of transition metals, which has several downsides. Recently, metal-free alternatives relying on electrochemistry have gained interest. One example of such a reaction is the oxidation of tetraorganoborate salts that initiates aryl-aryl and aryl-alkenyl couplings with promising selectivities. This work investigates the mechanism of this reaction computationally using density functional and coupled-cluster theory. Our calculations reveal a distinct difference between aryl-alkenyl and aryl-aryl couplings: While C-C bond formation occurs irreversibly and without an energy barrier if an alkenyl residue is involved, many intermediates can be identified in aryl-aryl couplings. In the latter case, intramolecular transitions between reaction paths leading to different products are possible. Based on the energy differences between these intermediates, we develop a kinetic model to estimate product distributions for aryl-aryl couplings.

Funding

Theoretical Chemistry of Unbound Electrons

European Research Council

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DFG grant 2227/2-1

Fonds der Chemischen Industrie

Erasmus+

Ludwig-Maximilians-Universität München

SFB 749:  Dynamics and Intermediates of Molecular Transformations

Deutsche Forschungsgemeinschaft

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History

Email Address of Submitting Author

florian.matz@pci.uni-hannover.de

Institution

Catholic University of Leuven

Country

Belgium

ORCID For Submitting Author

0000-0001-5670-8057

Declaration of Conflict of Interest

There are no conflicts of interest to declare.

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