Green synthesis of symmetric dimaleamic acids from dianilines and maleic anhydride: behind new bidentate ligands for MOFs

We herein report the synthesis and characterization of six α,β-unsaturated dicarboxylic acid ligands with different phenyl spacers, and two ligands with a biphenyl and anthraquinone spacers. All these dimaleamic acids were synthesized in 16 to 99% yields via a base-catalyzed maleimide ring opening in water (ligand 2), or by a di-N-acylation from the corresponding diamines and maleic anhydride in acetic acid (ligands 4, 6, 8, 10, 12, 14 and 16). These reactions were performed using green solvents, while requiring minimal work up procedures, making them suitable alternatives to access these types of bidentate ligands quickly, which can be used to fabricate new metal-organic frameworks (MOFs).