Base-Catalyzed Dehydrogenative Coupling of Formate Anions to Oxalates: Effect of Alkali Metal Cations

Herein, the influence of group 1 and 2 metal cations on base-catalyzed dehydrogenative coupling of formate to form oxalate is reported. Treatment of sodium formate with a various types of bases (group 1 and 2 metal carbonates or metal hydroxides) revealed that, compared with carbonate salts, group 1 metal hydroxides behaved as efficient bases for the formation of oxalate, in which cesium hydroxide (CsOH) showed the best catalytic activity. DFT calculation for the reaction mechanism suggested that its kinetic advantage was generated from not only an increase of basicity but also destabilization of the intermediate species due to Na/Cs mixed cation system. The effect of cations in formate salts were also discussed both experimentally and theoretically, in which the yield of oxalic acid depended on thermodynamic stability of both products (oxalate salts) and intermediates.