Scheme 2:

(A) Synthesis of methoxyterephthalates from hydroxyterephthalic acids. (B) Synthesis of methoxyterephthalates from lignin-derived 4-hydroxyacids. (C) Optimized conditions for the electrochemical Ni-catalyzed carboxylation of G and S phenols in batch and flow. Yields are based on 1H NMR spectroscopy, unless otherwise specified, using 1,3,5-trimethoxybenzene as an external standard. Flow electrolysis was performed under recirculation with a flow rate of 30 mL min−1.