Electrochemical Asymmetric Diacetoxylation of Styrenes Mediated by Chiral Iodoarene Catalyst

Organocatalysis with chiral iodoarenes has emerged as a powerful approach for performing enantioselective transformations. However, it suffers from the need to utilize stoichiometric amounts of peroxy acids or similar high energy oxidants. Electrosynthesis enables eliminating stoichiometric redox reagents by replacing them with electric stimuli. In this context, an electrochemically-promoted variant of the chiral iodoarene-catalyzed asymmetric diacetoxylation of styrenes was evaluated. The screening of reaction parameters established a set of conditions under which, for the first time, an enantioselective electrochemical oxidation mediated by a chiral iodoarene achieving a catalytic turnover has been accomplished. The reaction was applied for the synthesis of an array of products in 15-60 % yields and 0-84 % ee. The modest efficiency of the electrocatalysis was traced to a partial direct oxidation of styrene substrates leading to racemic products and undesired dimeric side-products. Cyclic voltammetry measurements demonstrated that such outcome originates from a somewhat difficult electrochemical oxidation of the applied iodoarene catalyst. Present work provides important insights and implications for the design of more efficient electrocatalytic systems employing chiral iodoarenes as mediators.