Direct Photochemical C-H Carboxylation of Aromatic Diamines with CO2 under Electron-Donor- and Base-free Conditions.

We report the photochemical carboxylation of o-phenylenedimamine in the absence of a base and an electron donor under an atmosphere of CO2, which afforded 2,3-diaminobenzoic acid (DBA) in 28% synthetic yield and 0.22% quantum yield (Φ(%)). The synthetic yield of DBA in this reaction increased to 58% (Φ(%) = 0.47) in the presence of Fe(II). The photochemical reaction described in this work provides an effective strategy to use light as the driving force for the direct carboxylation of organic molecules by CO2.