Efficient electrochemical synthesis of phenylacetic acid derivatives: Utilizing CO 2 for sustainable production

Phenylacetic acid derivatives, including 1-naphthaleneacetic acid, hold crucial applications in various domains. Traditional synthesis methods often involve intricate steps or the use of expensive and polluting heavy metal catalysts. This paper presents an electrochemical approach for efficiently producing valuable compounds like 1naphthaleneacetic acid and other phenylacetic acid analogs through the reduction of benzyl halides, such as 1chloromethyl naphthalene, in the presence of CO 2 . At the same time as preparing phenylacetic acid, the resource utilization of CO 2 is realized. Six kinds of carboxy analogs were synthesized by potentiostatic electrolysis of benzyl halides in acetonitrile with CO 2 as a co-reactant and tetraethyl ammonium tetrafluoroborate as an electrolyte. The electrochemical reduction products were confirmed structurally through NMR, mass spectrometry, and other techniques. The Faraday electrolysis efficiencies ranged from 82 % to 94 %, with 72.5 - 92.9 % conversions. The study delves into the electron transfer mechanism using cyclic voltammetry and in situ FT-IR spectroelectrochemistry. The reduction process on silver electrodes under a CO 2 atmosphere was identified as an irreversible two-electron process, generating a monovalent anion that attacks CO 2 to yield the respective carboxyl analogs.