Coupling of Alternating Current to Transition-Metal Catalysis: Examples of Nickel-Catalyzed Cross-Coupling

Abstract

The coupling of transition-metal to photoredox catalytic cycles through single-electron transfer steps has become a powerful tool in the development of catalytic processes. In this work, we demonstrated that transition-metal catalysis can be coupled to alternating current (AC) through electron transfer steps that occur periodically at the same electrode. AC-assisted Ni-catalyzed amination, etherification, and esterification of aromatic bromides showed higher yields and selectivity compared to that observed in the control experiments with direct current. Our mechanistic studies suggested the importance of both reduction and oxidation processes in the maintenance of the AC-assisted catalytic reactions. As described in presented examples, the AC assistance should be well-suited for catalytic cycles involving reductive elimination or oxidative addition as a limiting step.

Nickel-Catalyzed Paired Electrochemical Cross-Coupling of Aryl Halides with Nucleophiles

“…In 2021, the group of Semenov reported an alternating current assisted Ni-catalyzed amination, etherification, and esterification of aromatic bromides. 50 Overall, the advantage of AC over DC assistance is pronounced for esterification and etherification and, to a lesser extent, for amination. Therefore, we will discuss this elegant research work in the CO/S bond formation section (vide infra).…”

“…Much less attention has been paid to alternating current (AC) electrolysis, where the flow of charge changes its direction periodically. The use of AC provides at least two advantages over DC electrolysis in paired electrolysis: 50 (i) transferring reactive intermediates between electrodes can be avoided, which prevents the dilution of the reaction partners and facilitates the reaction of the short-living intermediates; (ii) the frequency and the waveform of AC can be tuned facilely to achieve the best selectivity of reactions. Considering these advantages, in 2021, Semenov and Bortnikov applied this AC technique to the etherification and esterification of aromatic bromides with a significant advantage over DC electrolysis.…”

“…Considering these advantages, in 2021, Semenov and Bortnikov applied this AC technique to the etherification and esterification of aromatic bromides with a significant advantage over DC electrolysis. 50 As shown in Scheme 24, esterification of 4bromo-1-(trifluoromethyl)benzene produced the desired esters efficiently for aromatic-, aliphatic-, and Boc-protected amino acids (46a, 46b, 46c). Besides, other electrondeficient aryl bromides (46d, 46e) also reacted smoothly with Boc-L-proline in good yields.…”

Amination of Aryl Halides Mediated by Electrogenerated Nickel from Sacrificial Anode

“…More recently, Semenov and coll [14] . achieved nickel‐catalyzed electrochemical amination of aryl bromides using uncommon alternating current electrolysis.…”

“…More recently, Semenov and coll. [14] achieved nickel-catalyzed electrochemical amination of aryl bromides using uncommon alternating current electrolysis. The couplings were carried out under similar Baran's experimental conditions with glassy carbon rod electrodes in an undivided cell (Scheme 1b).…”