Advanced Electrochemical C–C Bond Formation Using a Michael-Type Nozaki–Hiyama–Kishi (NHK) Reaction

Herein focuses on using organometallic electrochemistry for the electrochemical allylation of dihydroxybenzenes and 4,4'-biphenol, employing a mechanism based on the Nozaki-Hiyama-Kishi (NHK) reaction. The NHK reaction, known for its nickel/chromium cross-coupling process, is applied to synthesize allylic alcohol adducts. A convergent paired-electrochemical mechanism is used, catalyzed by NiCl₂ in Bu₄NClO₄/DMF media, and optimized through a multiparameter Design of Experiments (DoE) approach. The study systematically evaluates reaction conditions, considering parameters such as electrode material and current density in an undivided electrochemical cell. DoE allows efficient screening, reducing the number of experiments while optimizing key factors affecting reaction yield. Various electrochemical cells are tested to refine electrode materials and analyze cathodic reaction kinetics. The highest isolated yield (94.0%) is achieved using the NHK reaction with a graphite anode and nickel cathode, highlighting the critical role of electrode selection. Theoretical calculations at the BP86/6-311G level assess the charge influence on the Michael acceptor's reaction site. This computational framework aids in understanding site-selectivity in Michael-type addition reactions, further refining the mechanistic insights of electrochemical allylation.