Asymmetric Electrochemical Alkenylation by Synergistic Chiral Primary Amine and Naphthalene Catalysis

Abstract

Abstract External tuning of enamine intermediate has significantly expanded reaction space of typical aminocatalysis. Notwithstanding the progress of chemo‐ and photo‐oxidation of enamine intermediate, electro‐oxidation was left as a much less explored area, in stark contrast to the prosperous renaissance of electrochemistry in recent years. Challenges mainly come from the reactivity barrier as a consequence of heterogeneous electron transfer and subtle stereocontrol in ionic electrolyte solution under the influence of electric field. Herein, we report asymmetric α‐alkenylation of carbonyl compounds using potassium alkenyl trifluoroborate as a model reaction to demonstrate the capability of primary amine catalysis under electrochemical conditions. By employing enamine redox mediator mapping (e‐RM 2 ) strategy, a new organic mediator, dimethoxyl naphthalene, was found to greatly enhance reactivity. Mechanistic studies uncover an ion‐pair interaction between protonated aminocatalyst and anionic substrate that accounts for the exceptional enantioselectivity. This catalytic system demonstrates the best level of enantioselectivities in electro‐oxidative enamine transformations so far.