Computational insights into electrochemical cross‐coupling of quaternary borate salts

Abstract

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. The 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 arylaryl couplings. In the latter case, intramolecular transitions between reaction paths leading to different products are possible. Based on the energy differences between these intermediates, a kinetic model to estimate product distributions for aryl-aryl couplings is developed.

Forging C–C Bonds through Intramolecular Oxidative Coupling of Organoborates – An Overview

“…Crossover experiments on electrocoupling reactions (Didier, 2020) 43 The group of Jagau further investigated the mechanism through theoretical calculations, providing insights into the key C-C bond-formation process. 44 Their results seem to point towards a -bond addition onto the dearomatized aryl structure (…”