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

we herein report the synthesis and spectroscopic characterization of six a,b-unsaturated dicarboxylic acid ligands with different phenyl spacers and two more new 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 1) or by a di-N-acylation from the corresponding diamines and maleic anhydride in acetic acid (ligands 2 to 8). These reactions were performed using green solvents while requiring minimal work up procedures, making them green alternatives to access quickly to these types of bi-dentate ligands, which can be used to fabricate new MOFs.