Pd(NHC) Electrocatalysis for Phosgene-Free Synthesis of Diphenyl Carbonate

Electrocarbonylation of phenol with CO to diphenyl carbonate was studied using a homogeneous Pd electrocatalyst. Various ligands were screened, and N-heterocyclic carbene (NHC) groups, such as 1,3-dimesitylimidazol-2-ylidene, were found to be effective for the electrocarbonylation. An in situ-generated NHC derived from a 1,3-dialkylimidazolium chloride was also effective for the electrocarbonylation, and 1,3-di­(tert-butyl)­imidazoline chloride was the most effective NHC precursor, with a stronger electron-donating ability to PdCl₂(MeCN)₂ electrocatalyst.