Electrochemical β-Selective Hydrocarboxylation of Styrene Using CO2 and Water.

The carboxylation of hydrocarbons using CO2 as a one-carbon building block is an attractive route for the synthesis of carboxylic acids and their derivatives. Until now, chemical carboxylation catalyzed by organometallic nucleophiles and reductants has been generally adopted particularly for the precise selectivity control of carboxylation sites. As another approach, electrochemical carboxylation has been attempted but these carboxylation reactions are limited to only a few pathways. In the case of styrene, dicarboxylation at the α- and β-positions is mostly observed with electrochemical carboxylation while site-selective hydrocarboxylations are hardly achieved. In this study, electrochemical β-selective hydrocarboxylation of styrene using CO2 and water is developed, in which the site selectivity can be precisely controlled between β-hydrocarboxylation and dicarboxylation without the aid of homogeneous catalysts. In this platform, water is used as proton source in the β-hydrocarboxylation of styrene where its addition results in significant enhancement of the selectivity toward β-hydrocarboxylation. This work provides insights into new strategies for site-selectivity-controllable carboxylation with CO2 using an electrochemical platform.